SteveC said:
I like the idea of having a discussion about this as a whole, but I don't think it will go particularly well that way...we have discussed it before, and it didn't go well. The player in question basicly just said "I'm going to be true to my character come heck or high water" and left it at that.
Yeah, that can be really annoying. Perhaps it wasn't presented to him in a non-threatening way. If he feels ganged up on or attacked (for any reason), he'll put up his defenses. It won't matter if you tell him the meaning of life, he won't hear you and will just say no.
Ask him, since he's making a new character this week (and every other week), to create one that wants to spend time with the group. Then be true to the character, come heck or high water. He could be there for any number of reasons (family obligation, hero worship, life debt, etc). Just as long as he's there.
That's the obligation of the player. Usual argument against this? "Well, it's not like the whole world wants to spend time with the party. If they did, we'd have more group members, right?" And your response is, "The world isn't looking to spend time with us. Right now, only one person is. You. The only question is why."
It's the players' job to get with the party and stay there. It's the DM's job to give them something to do. While sometimes these overlap (like any good friends, they help each other out) that doesn't absolve the other of their responsibility.