Re: If you have a problem with IC actions of players....
As is obvious just from this thread, people have very different ideas about what "in-character" and "out-of-character" mean, so as gladiusdei says, it really depends.
I once expressed to a player that I preferred that they not play their character in a particular way, and the player informed me that the character was not in his control and that if something bothered my character then the character should deal with it. He didn't out-and-out tell me to have my character argue or fight with his, but that seemed to be all the choice he was leaving me. I chose to ignore the character to the extent possible, for as long as I remained in the game. A passive-aggressive decision, but I didn't see much alternative.
And I can see the point that it's a bit silly for a player to be bothered by what a character in a game is doing, as long as rules are being followed. Some might play that way, but not everyone does, and sometimes players use their characters as proxies to get at other players. There might not be actual malicious intent, but that can only be determined (if it can at all) by discussion with the player.
I can also see the point that a player might feel that accurate and faithful roleplaying requires a particular set of behaviors. This, of course, is why it's common for GMs to set alignment restrictions, so players feel neither compelled to have their characters behave nor excused from their characters behaving in certain ways. I don't personally feel that a player is ever required to run their character in a way that ruins anyone else's fun, but I know not everyone would agree with me.
A person's ability to adjudicate a game doesn't tell me much if anything about their ability to adjudicate real-world interaction. It seems polite to me to inform a GM of any unresolved disputes between players or play styles (and I did so in the game I mentioned above), especially if it's going to result in some oddness, but unless the GM has a proven track-record in the form of trusting relationships with the players in question, there seems little reason to involve them. A GM is, at most, the final arbiter of the rules and who gets to sit at the table, and sometimes doesn't even have that much power or control.
The only thing I'm sure of is that players and GMs should either be able to trust each other, or not play together. If one can't trust that everyone else involved is doing their best to enhance the game for everyone, then I don't see that as a viable game, even if no one is actually being malicious.