I think my problem is that I'm way too diplomatic, way too accommodating in dealing with these people. George L.'s advice to "start acting better than the other guy" is something I've always done -- especially with obnoxious higher-ranked aikidoka -- but doing so, it seems, often only encourages their obnoxiousness. I'm thinking now that, with certain individuals, giving as good as I'm getting is more appropriate than turning the other cheek.
Ok, so taking the "high" road isn't very enjoyable. It's fairly obvious from looking at the world in general that "goodness is it's own reward" and "crime doesn't pay" don't operate much in reality.
If you are really getting frustrated there may be some satisfaction in dropping your obnoxious partner like a stone. Or go ahead and shut him down, show him that he isn't as good as he thinks he is.
All of this can be quite satisfying, I'd be the last one to say it isn't. When I first started Aikido there was a yudansha who pretty much dominated me and everyone else in the dojo. I don't think I ever threw him without him first making it apparent that he could have stopped me. I was terrified of him and spent a lot of time trying to be on the other end of the mat. Then he went away for a while during which he had an operation. When he came back he wasn't as strong as he had been but he wanted to resume the previous relationship in which I was clearly subservient. But he was weaker and i had gotten better... One night we were doing shihonage. He went to shut me down, as usual, but I suddenly realized that I had it. It wasn't pretty but I did have it. He couldn't let go of his need to be the dominant partner and wouldn't take the fall but I completed it anyway and ripped his arm out and put him off the mat for another six weeks. After that he didn't screw around with me any more. I never felt the least bit guilty about it because he was light years better than I was and could have chosen to take the fall at any instant but his ego wouldn't let him. As far as i was concerned, he hurt himself. Anyway, it was a useful lesson for me. But it isn't my "default", I have to get pushed pretty far before you are going to see that side of me.
So possibly, it's part of your training, as Sczepan points out, to learn to stick up for yourself. But I have to say, after all these years, that it seldom improves your position much ( as much as it feels good to dish out what you are getting). Pointing out to seniors that they aren't as good as they'd like to think can actually be dangerous. They are apt to get you back by hurting you to show how superior they are (this applies even more to some teachers). It almost never improves their attitude. It also doesn't usually improve your position with the teacher who, after all, gave them the rank in the first place. So how much fun is it to go to the dojo each night knowing it's going to be a pissing contest to see who can be Alpha dog?
Best thing is to:
a) avoid training with butt heads as much as possible; if there are too many, well maybe that says something about the dojo and you should consider leaving... and
b) rather than point out that other folks aren't as good as they think by acting as badly as they are, train until they can't stop you, which is of course, what you are really there for. Train more and train harder. The problem then takes care of itself. Not only do people stop screwing around with you but this approach will enhance your place in the dojo and with your teacher.