Re: What do you do when a student is acting rudely in your class.
Rudeness comes in all sorts of forms.
I've had people show up with a little red book loudly proclaiming what I was doing was not Aikido to an actual physical assault. In both cases they had not actually crossed the threshold of the class so to speak so getting rid of them was no issue.
The most difficult was in Japan with a 30+ Japanese gentleman who the more he took the class, the more frustrated he became, to the more he ended up lecturing my Japanese partner on his shortcomings as a teacher. Finally things were said and he stormed out (the gentleman not the partner - of course the partner was also a gentleman). Strangely a few months later he came back and apologized having the same experience with different Aikido teachers but we declined his request to continue.
So - besides a story - if you feel that something must be said you are probably right and the longer you leave it the worse it will get. If you are not the head of the school it is not your place to kick someone out but you should tell whoever is your opinion. Most people will fool themselves into saying its not that bad until others help them see. Most people want to see the dynamic of their group being constructive.