How To Handle Troublemakers

This topic comes up a lot. How do you manage people causing problems in your community?

There are remarkably few options.

Do nothing. There is a difference between causing friction and doing irreversible damage to the community. If they’re in the former, let it go. You’re not the opinion police.
Kick them out and ban them. If they are doing real damage to the community, inciting hatred, planning terrorist atrocities, engaging in illegal activities, or insulted your parents – boot them.
Suspend them. You don’t always have to kick people out, just suspend them from posting for a few days. Do this often enough and they will either lose interest in the community altogether, or recant their past behaviour and work for the common good.
Punish them. Every time they do something wrong, reduce their karma points, prevent them from posting, reduce their post counts, change their profile picture, or simply edit their messages to something funnier – or just delete them entirely.

Reason with them. Not you, the community. Ask a few regular members what damage they believe Mr. X is doing and present quotes (anonymously) to the person. They might see the light of day.
Sidetrack them. Put them in charge of incredibly irrelevant projects, unimpressive forums, or agree to let them voice their opinions in their own column/forum.
Let the community decide. “Well beloved community, do you want this member to continue doing what s/he has been doing? Or should we kick him/her out?”
Bribe them. If you stop doing {x}, I’ll give you your own forum, VIP status, extra karma points, a regular column.

Two more thoughts. (1) Be careful that the behaviour you don’t like and the behaviour the community doesn’t like align. (2) Just because the community doesn’t like one person’s behaviour doesn’t mean his behaviour is wrong.