Don't argue with a fool. It sometimes makes it hard to tell the difference.
However, in Marshall's case, "HA HA HA HA..." makes it easy to spot the fool. As I once said, trying to talk sense with him is like trying to get through to someone who's brain dead and on life support. No matter how hard you try you just can't get through. The most humane thing to do to our "Terry Schiavo" is to simply pull the plug. If that means putting him on ignore, then pull the plug and he will fade away.
There are days I contemplate putting him on ignore, but then I get into an evil mood and realize I enjoy watching a pathetic loser dig himself deeper and deeper into the dung pile. When I start to lose faith in myself I look at his posts and realize I'm not so bad off afterall. I should pity him, but I have not overcome all my weaknesses yet--and it's more fun to just laugh at a jackass at times.