ryback

Well, to be honest, the more I read of this thread, the more I get the feeling that people tend to turn a dojo into a kindergarten, as if they never progressed since that age.
A dojo is more or less a simulation of a battlefield and the best thing we should do is treat it with the appropriate respect before someone gets hurt. There is no place for irresponsible acting inside a dojo.
And when i talk about irresponsibility i'm not refering only to the guy who is causing the trouble, but to everybody else as well.Sure, a student like that can spoil the atmosphere of practice and the feeling of harmony. But then again,an attacker on the street will not be harmonious either, so dealing with a guy like that can be good practice as well.
So in my opinion,the only one wasting his time is the troublemaker.I don't think that one should try to talk to him, or moan to the Sensei about him.If one is a sempai there is a reason why he has that rank and position.It means that he must be able to deal with situations like that during practice in the best posible way,according to the situation at hand.
The way I see it, the different ways of dealing with a guy like that, range from ignoring him (when possible) to landing him hard on his ass (when...needed), and everything in between.
Aikido is a martial art, so we must treat it as such. Dont let your practice revolve around a single person,he shouldn't affect you anyway.