Personally as a guy I'd take offense if some other guy told me something unless it was a close friend. As for what you can do, not much really...even if you told him you didn't put him up to this he'll just assume you've been talking bad about him behind his back and people will think less of him.
I agree with alice444's advice.
Me: 35|WAW: 38|D: 6yo | http://tinyurl.com/2dxx7m6 Feb 2006, left, came back in two weeks Aug 2006, left again Apr 2007, filed for divorce Dec 2007, reunited Mar 2010, moved out, filed again