I've resorted to the multiple slay idea. Slay at the offense and say why. If they continue to be a douche then continue slaying at the beginning of the round. Drove off 3 asshats doing that and the server never had an issue. Easy to do when you are upfront about it. I think people make a stink when a ban comes out of no where and their "friends" complain on the server after it happens.
I used to love the ma_cexec for that reason. Except I'd bind their mouse1 to "kill" so every time they tried to shoot, they'd die.
I was also a fan of slaying at the beginning of every round until they left. Until I got chewed out for that as well.
i hate valve for nerfing that command although there were admittedly some pretty nasty things that could be done to people. (unbindall, ma_browse meatspin.com (trust me you dont want to go to that website)
but
bind mouse1 "say BANG!" was epic