GM interference depends on the player argument. Generally though, a good GM will want to step in and help resolve any disputes simply because arguments are not fun for the rp and group as a whole. I mean, Brovo summed it up pretty succinctly.

[quote=Brovo]That being said, when two players argue, you can either let em' go at it to the inevitable conclusion that one or both leave, or you can step in and tell them both that continued argument warrants being dropped due to ruining it for everyone else, over what is likely a petty dispute that can be resolved amicable. If they refuse to listen and continue to argue, drop them. If they continue to post in your thread, request a moderator to remove them and give them a slap on the wrist.[/quote]

I find player arguments sometimes fascinating to behold if only to see how people react to problems and situations like that, to guage their personality, and be aware of how probable they might present future problems whether it be through causing them or responding to something with an unreasonable, negative attitude etc. At the point where we are in my rp I only accept players I personally invite, and one of the criteria I search for in a player beyond simply rping skill, writing quality and posting consistency, and almost more importantly actually, is whether or not they're a decent, communicative person who can react to disagreements and constructive critcism well.