I don't to be honest. Hell, since everyone seems to be rude here, I don't even start the game with a 'have a good game' anymore. It's a shame that chess ethics (giving a hand before a game) don't translate well to internetplay.
Rude live chess opponents

I play longer time controls and have never had a problem with a rude opponent in the four years+ I have been a member of chess.com.

Finish the game and block them. Depending on the offensiveness and my mood I might also report them to the staff.

With jerks you have three options:
1) Avoid
2) Ignore
3) Fight back.
Three is silly because an impartial observer would be inclined to think both of you are jerks. Two is your option if One is not available. Therefore, simply turn off chat and block the person -- quite simple.

I turn off the chat or ignore them. If someone makes an offensive post on my page, I report them (along with a screencap of said image and delete the post.) If they repost again, I'll re-report them and block them.

I play longer time controls and have never had a problem with a rude opponent in the four years+ I have been a member of chess.com.
Makes perfect sense. I play OTB with 2 and 5 min players who talk so much trash. But you are right. They think long time controls are boring. You can usually weed them out that way.
How do you guys react when your opponents send offensive chat?