I know exactly how you feel. In a game I was in we had a player that would repeatedly shoot down our ideas without contributing ideas of their own. We'd spend literally an hour listening patiently while they would shoot down, in detail, any idea we came up with. I'm not talking in game conversation, this was total out of character. However, as we all were patient and let them get it out of their system trying not to cause too much OOC resentment. That game came to an end and we all re-rolled and started anew.
The player's new character was rude to other characters, it seemed to the degree of actively taking jokes on the chin with a group that up until that point felt it was okay to joke with each other. Then they started slipping into their old habits, player wise, telling others how to play their characters, relentlessly shooting down any idea the others had, again without a contribution. Now, as a player in a roleplaying game you make allowances for OOC personality conflicts and you don't take OOC actions IC. However, once the player is given the option of "stab the team in the back," or "take your lumps and just roll with it," and they take the former. Its then that the "one of the players" shields come off. So all the rudeness and anti-social activities of the -character- are not overlooked and acted on as the characters would react. The players having held back their IC because of OOC "one of us" shields all players should have.
It then comes down to "What would happen realistically." While I personally don't like inter-PC conflict and do my best to avoid it, sometimes someone's In character actions have in character consequences. Its only their out of character "member of the gaming group" that prevents the IC reactions from happening.