Realism? What would you do "realistically" if a coworker stole from you? Kick the bastard out, that's what you'd do. And if you were Zog the Archmage of Energy, you'd probably incinerate him as well.
You see, there is a social contract between players: You don't abuse meta-game forces that keep our characters together (I mean meta-game in the neutral, descriptive sense). Because you and some friends are gaming together and all have characters, the characters are lumped into a party, even though realistically Sir Otto Von Ratzenbanger the Highborn would probably have nothing to do with grubby Roguely MacStealingstuff. We, as D&D gamers, ignore a fair amount of "realism" for the sake of making the game work.
But stealing/harming other PCs takes betrays that system and takes advantage of it, to the detriment of the game. If you feel your character should be free to steal from the others, then the others should be free to say "we don't want your character in the party. Roll up a new one."