Really this question is 'chatty' and therefore doomed to be closed, however...
No it is not rude!
Drafting should be taught at school as part of a Cycling Proficiency Test so that some conventions are established. This would encourage people to cycle together, taking turns up front and doing so more efficiently. Elbow twitches to get the guy behind to take a turn need to be an accepted convention and ladies not wanting a 'crafty drafter' behind them should be able to use this if they are not happy with whomever is following them.
Every time you draft someone that thinks it is rude you are helping to break down their 'hostile' attitude. The truth is that one should be flattered to be drafted, particularly if you are old, with a rubbish bike or carrying loads of stuff. Drafting goes on, whether you like it or not, and the reality has to be lived with. If you really do not want to be drafted you could always put a big sticker on the back of your seat saying 'DO NOT DRAFT!' - 'L' plates for the bike as it were.
Clearly there is the problem of stopping suddenly for some drafter to go into the back of you. However, there are ways to deal with this potential threat. First of all, think of who is the most scared of a crash - you or the guy behind? The guy behind is not going to be right on your wheel if they are not experienced enough to draft close up. If they know what they are doing and know every pothole in the road then they might be up tight.
By convention, in a crash, it is the guy that goes into you that is at fault. You could have a car door or other instant stop requirement, however, if some cyclist goes into the back of you during such an incident, you do have to ask yourself a few questions about your own riding and not just blame the other guy. Even though the roads are full of hazards it is for you to anticipate and ride accordingly.
As for 'providing a wheel' there should also be some convention to signify that this is being offered. Cut too close in front of someone and you can have some wheel entanglement, go past too fast and they ain't going to make it. When riding with a weaker rider and wanting to put in a good collective time successful drafting makes all the difference and it really should be taught at an early age.
Incidentally, my 20" wheel 'shopping bike' is excellent for drafting. It is about a foot shorter at either end and that extra bit of proximity really helps whether up front or behind.