Durge would have been better as a human. I mean, why would a giant mutating blob that wears a helmet hate Mandalorians so much.
Let's indulge ourselves in the history of the Mandalorians, shall we?
First off, the Mandalorians were hired to fight AGAINST the Old Republic (by the ancient Sith, I believe). They were defeated by the Republic fleet led by Revan and Malak, which, in turn, became Sith. So who knows. I don't see why ol' Durge is fighting against the people that were technically on his side before he reawakened. Ok, I'll stop now... lol