@Ironclad
1. Everyone else is preoccupied with fighting while Rokudou calls Yagen out.
2. A lot of these guys don't care that he's a backstabbing asshole either way, as they're more obsessed with him being their strong and manly leader. They're the kind of guys that will do anything to win, so it's not like they care about morals.
If that's not good enough for you, I don't know what else to tell ya.