Is this bike suitable for men?
Argenti and Kaz both are correct, but let's dive a bit deeper into women's specific design (WSD). Their answers allude to an old paradigm of WSD. It appears to be based on anthropometric measurements collected by the US Army that was described as "decades old" in a 2017 interview with Stephanie Kaplan, a product manager with Specialized. These data showed that the average woman had relatively longer legs and a shorter torso than an average man of the same height.
Operating from those data, manufacturers would typically make a WSD bike that had a relatively shorter top tube than a men's bike in the same size. Obviously, they would also offer smaller sizes (the average woman is shorter than the average man, which is probably beyond debate), women's specific saddles, and narrower handlebars.
Compare Boardman's current MTX 8.6 women's bike to the men's version of the same bike, you can see this paradigm in operation. A frame's reach is basically how long it is, and its stack is basically how tall it is. I'm comparing two frames whose absolute size is relatively similar below.
Medium women's MTX8.6: Recommended rider height 157-170cm Stack 615mm Reach 387mm
Small men's MTX 8.6: Recommended rider height 160-172cm Stack 602mm Reach 391mm
Basically, the women's frame has a more upright position, and it's slightly shorter. So, Boardman is still operating out of this paradigm.
Some manufacturers, like Trek and Specialized, have gone away from that old paradigm. Notably, in the interview I linked, Specialized had current data from in-person bike fits in person through their Retül service; Retül was an independent bike fitting company that Specialized bought. They said that in that data, they didn't see any justification for this split in geometry. So, their women's specific bikes have the same frame dimensions as the men's bikes of the same size and the same equipment specifications. They're painted in more pastel colors. The contact points differ. The crankarms may be shorter on women's bikes. I can't be bothered to link, but you can compare the specs yourself.
Not all manufacturers are going this route! This 2017 review of Canyon's women's CF SLX bike said that:
Canyon’s online ordering system collects body dimension data from all its customers, including height, weight, and leg and arm length. While this information helped people identify which frame size to purchase, the data — now over 60,000 entries strong — also gave the engineers at Canyon a clear picture of the biometric and anatomical make-up and requirements of its customers.
That data not only showed some fundamental differences in the male and female dimensions, but also the exact nature of those differences. Most notably, Canyon found that, contrary to popular belief, women’s legs are only marginally longer than men’s legs for a given height. However, their arms are consistently shorter (by 2cm on average) for a given torso length. According to Canyon’s data, women also tend to be shorter and lighter, and they have greater pelvic flexibility.
Taking all of this data into account, Canyon designed the new WMN frame geometries with slightly higher stacks and shorter reaches compared to the unisex frames. The WMN frames are also lighter than the unisex versions for a given size, feature more aerodynamic profiles, and the size range now extends down to 3XS to cover rider heights as low as 152cm (5’ 0″).
Who's right, Specialized or Canyon? That may be impossible to truly answer. The people who get fits from Retül are different from the people who shop online for Canyon bikes, and both are different from the general population.
There is another dimension to the question "is this bike suitable": capability. Women could be looking for a less aggressive cycling position or an otherwise different cycling experience than men - or manufacturers and retailers could incorrectly believe that women are looking for this. I think this doesn't apply to your situation, but it's worth discussing.
Some of those issues are discussed here and here. For example, the Specialized Allez and Dolce are entry level road bikes, but the Dolce is a women's frame and the Allez is unisex (in the past, this definitely meant designed for men; currently, it may still have this meaning). The Dolce has less aggressive geometry (more upright, steers slower) and has more vibration damping features than the Allez. This may make sense for entry-level female vs male riders. Canyon, in the quote above, said that its women's frames use lighter (but more aerodynamic) tubing than same-size men's bikes. I am guessing their assumption is that on average and controlling for height, women will put out less power than men. They don't need heavier tubing; they won't benefit from the additional lateral stiffness, and they will benefit from greater vertical compliance. (Note: frame stiffness may not matter that much for any rider, but this is another story.) Maybe this is a wrong assumption, but I think I can see some face validity here.
Basically, we don't want women's bikes at all levels to be crummier versions of the stuff available to men. For example, I recall than the 2010 Specialized S-Works women's shoes had a lower stiffness rating than the men's S-Works shoes. - I know this because I have a pair of the women's shoes due to fit reasons (discussed below). We do not want women to be restricted to poorer versions of men's equipments. Even if your average woman wants a less aggressive cycling experience than the average man, a) this may change over time, and b) there are women who race at the professional level, and they can put out far more power for much longer than you, I, or probably anyone else on Stack Exchange. We want manufacturers to equip athletes according to their capabilities. This may not matter for the bike you want to buy, however. Moreover, I can't tell if the women's version of that bike was equipped differently than the men's version, as I can't find the model information on Google.
Back to the original question! Does the frame fit you? You can move the stem lower on the steerer tube if the stock position is too high for you.
Its components aside from the saddle may have been identical to the men's version. Hence, color aside, this bike is potentially suitable for some men, perhaps even many men. It will not be suitable for all men. We can't say for sure if it's suitable for you personally. That is what matters. If it fits (or it can be adjusted to fit) and the components meet your needs, then you could consider it. I will assume that Boardman specced a women's saddle, and it's more likely you'd want to change that (but it's not guaranteed). If so, I suspect it will be wider than the average men's saddle. I'm not familiar with front suspensions, but I guess it's possible that the suspension they chose was selected for the average weight of a female rider in the height range it was designed for. If you're heavier than this, it's possible you might find it's too compliant for you (i.e. your weight pushes it down more than it was designed for). This is speculation on my part.
Getting into the social aspects of WSD bikes is going to be primarily opinion based, and thus not really suitable for discussion on Stack Exchange. I will say that some fairly knowledgeable cyclists will know you're on a WSD frame. I think that most of these people would not judge you for it. I think that those who do judge you are doing humanity a disservice. The average person on the street probably won't know. The average rider I met never made a remark about my ladies shoes. The distinction between men's and women's paint schemes may be getting less distinct. Besides, pastels may well come into fashion for men. You could be setting a trend. (My shoes were all white and they matched my bike.)
As a side note, I'm a 5' 5" male cyclist. My bike is white with pink accents. I have a pretty long torso. I'm 1 inch taller than my wife, but my hips are actually a bit lower than hers. I have actually worn one pair of women's specific Specialized shoes because the last was identical but for the tighter heel cup, which fit my feet.
So, while I'm proportioned more like a stereotypical male under the old WSD paradigm, issues of fit definitely resonate with me. I can typically ride the smallest unisex bikes of (I think) all major bike manufacturers, although their seat tube angles are a bit more slack than I prefer. This typically causes some toe overlap, which isn't relevant on road bikes, but may sometimes be an issue off road. Also, a lot of shoes don't fit my feet well!!
Generally women's specific geometry bikes tend to have less effective reach (horizontal distance from bottom bracket to bars), either through a shorter frame or shorter stem, as women tend to have proportionally shorter arms than men.
if the geometry works for you, then it's fine. That bike has a fairly short stem so you could replace it with a longer one if you need to.
Boardman have a page which tries to explain what they mean by a woman's bicycle. See here.
This means that with our Women's range we use the same frame design and only minor changes to the geometries of our men's bikes, but offer smaller sizes and tailor the contact points to suit the needs of female riders.
You cannot tell by looking at the photo. The bike does have a sloped top bar, which reduces the SOH (stand-over height). But that amount of slope is seen on plenty of bikes sold as men's.
Men are not all tall. If a couple are shopping for a pair of bicycles, and she is taller than he, does it still make sense for him to get a men's bike and her a women's?
I'd use this bike. The light blue frame finish doesn't look particularly feminine, especially with all the black trim; it conveys light sportiness. Moreover, the brand has "man" in its name (what is more, unprefixed by "wo") if anyone still questions the bike's masculinity.