Amir0x saved my ass on a couple occassions so he's cool in my eyes, but this is just strange. I can't help it stems from his childhood and family. He sounds like someone who didn't get much love or respect as a little kid, and he grew up to be this big guy who's usually nice but can get rather violent if someone disrespects him like he was when he was younger. He realizes this, so he wants to give his sisters all the love and support he never had as a kid, because he doesn't want them to grow up like him; he mentioned he can't stand his sister's fiance, and it sounds like he feels this guy is in the way of this. Sort of reminds me of in Scarface where Tony loved his sister to the point where he didn't want to see any other creep touch her, even his best friend.
I hope things work out for him because he's got lots of stuff going against him. Seems like there are plently of people in NY like that, and many who aren't nearly as nice as Ami; I hope he doesn't wind up refusing to "back down" from one of those nuts, and runs into the wrong one