I'm always torn in situations like this.
Small confession:  I'm a functional sociopath.  I don't actually "like" almost anyone.  I'm not really capable of it.  Forming positive emotional bonds isn't impossible, but it's very rare and very hard.
To cover and compensate, I try to think, "What would a nice person do here?".  I am not, by nature, a nice person, you see.  Again, it simply isn't possible.  I have to work at it.
So a nice person wouldn't throw the clown out.  He/she would try to gently convert them, show them that there's fun to be had without being an attention whore or a show off.  Experience tells me this route has a really low success rate, but like me making friends, it's possible.
Also, a nice person wouldn't bulldoze a decision over the other people at the table.  Even if it's one they could get behind, it sets a bad precedent, and the shadow of that abuse would haunt the game for a long time.  So the hard, cold-blooded calculation says don't be hard and cold blooded. 
So my options are, be the nice person and live with the situation as best I can, or be the manipulative sociopath and not just let him run unchecked, but subtly encourage him until he crosses the line and people start threatening to leave if he stays.
If I skip the "subtly encourage him" part, the end result is the same, it just takes longer, stretching out everyone's pain.  Not very nice, in the long run.
I try really hard not the be that sociopath.