Imagine what would have happend if the guys had surrounded him and beat him to a pile of mush. Seems to me he knew what he was up against and prepared accordingly. He even consulted with the cops.
That's the problem- he didn't consult with the police. It says the girls' disappearance was reported to police- that's it. Once he found out where his daughters were, he should have phoned the police in Durham and reported they were at an underage drinking party. But he didn't do that. He took the law into his own hands. Luckily no one was injured or killed. By the way, everyone, whether it's a bunch of frat guys or the little old lady who lives in a shoe, has a right to protect their home. Since he entered their home uninvited, they had every right to throw him out or hold him until the police arrived.