Rage - not just for my Barbarian

I just found out something regarding one of the other players in my game that makes me FURIOUS. Backstory - he is playing a mage, who has a fighter-type-class bonded to him as his bodyguard. This bodyguard is a woman, and basically his slave and property (though she willed it), and they're in love. She's also pregnant, and he's the father. Now, apparently he didn't tell anyone in his family about this, because they arranged a marriage for him and now he's married to some other chick. My character is angry because she considers his bodyguard a sister, and my girlfriend's character is pissed too, for the same reason. They are not just going to sit back and watch her be hurt by this. My character is also not the most...rational of people, so she doesn't understand that its not his fault. But he also hasn't stood up and said anything about it, so both my character and my girlfriend's character have been acting very standoffish and angry at his character.

And he has been taking it personally, has threatened to kill our characters, and is all angry that we're "butting in," as my DM told me.

What a stupid FUCK!!!!!!!!!!! What does he expect us to do, just sit there with our heads in the sand? D&D is about ROLEPLAYING! THAT IS WHAT WE"RE DOING!!!! Our characters would be upset by this, so we're going to play them as upset. Just because HE doesn't know how to roleplay doesn't mean that we should all refrain from doing so. Expecting us to play our characters incorrectly because HE'S uncomfortable with the situation is bullshit. And he's angry enough about this to warrant my DM telling me. What a shithead. Oh, and I'm sure he's going to turn into even more of a whiny bitch because when my character finds out that he actually fucked this new wife of his, and hasn't talked to his girlfriend/the future mother of his child at all about the situation, she is going to FLIP SHIT. I had this planned before, so I bet its going to look to him like I'm just taking out my out-of-game rage on him, BUT THAT IS WHAT MY CHARACTER WOULD DO!!!!!

And now I really need to go to bed so I can get through work and driving 6-8 hours to my mother's tomorrow. Ugh. I just needed to get that off my chest.