I'd send him a PM saying what you are saying here.
If he feels he is right (i.e., the other guy really did lie), then the ball is in his court as to whether he wants to make such statements.
My opinion...truly wealthy and successful people don't worry about what is being posted about them on Internet forums and aren't wasting their time suing.
Keep us posted. If the guy really does sue, I'd love to hear about it.
One of my favorite quotes I remember from a Journalism professor was something like: "Anyone can sue anybody else. The real question is can you win."
As for the free speech issue, I love when users try to cry about that. Bottom line, it's your forum. If you don't want the mess on your site, it's your call if you want to delete it.
