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.