A Good Name
How much is your name worth to you? Would it bother you if your reputation were stained, not through something that you have done, but because of a smear, a lie, put on you by someone else?
I've been there, and it doesn't feel good.
If you treasure your good name, I doubt that you would be the one impugning someone else's reputation, as you wouldn't want to be known as "that" guy.
Go a step further. Don't echo "that" guy, don't broadcast his dirt, even if it is in line with your prejudices.
Be honorable. Prove yourself worthy of everyone's good impression of you.
You will feel good, and be able to look in the mirror without cringing.