Should another GrimShady pop up again, I'd like to offer some guidelines for you guys to follow:
#1. Completely IGNORE him. Don't bother AT ALL with replying how stupid he is, how dumb his post is, how offensive his post is, etc. Nothing. Rate it down and let it fall below sub-default and don't even give it a second thought. Seriously.
#2. Should you reply and attract his attention, causing him to target you, completely IGNORE him. Make a separate post denouncing involvment with him and then completely ignore any replies he makes, no matter how inane or flaming it may be. And then move on.
#3. Report things that should be nuked by e-mailing me with a link or his user ID. Click on the user's name and it will take you to their profile. In the URL you can find "user=1234567". E-mailing me with "go click on any post in the X forum" means it will take me longer to take action because I will have to read through the board to find what you're referring to. (E-mail is better than PM)
Above all, IGNORE trolls. All they want is attention.