Everyone knows you bring your friends over to watch you beat your wife or screw your sister in Mississippi.
Seriously, probably so they can all say she started/deserved it if she decided to speak out.
Maybe to stand watch to make sure nobody comes into the house to intervene.
shareI think that's the correct answer. Also, Pell was one of those guys who acted real big in front of his group of friends, but get him alone and you realize what a coward and wimp he really was. Kudos to Brad Dourif for a great performance of a really despicable character.
shareThe sheriff told him to go home and the unspoken message was that his wife was giving away their secrets.
Beating her up to punish/silence her was necessarily a group performance to assert his standing and ability to prevent further leaks. If not, he could have taken the fall for the group and been ostracized.
He may have even viewed it as weirdly protective, too, because if he doesn't beat her up there's some chance she gets brutalized by the other KKK guys instead. So, beat your wife up or maybe your Klan buddies rape the shit out of her instead and send you a message that way.