Posters keep saying "the NFL will accept wife beaters so whatever Willis might have done cant be as bad." NFL teams don't particularly care if you are a bad person. What they care about is availability. For example, injury-prone guys nearly always drop in the draft (even if a guy has a torn acl it's not necessarily a negative, but if he was always missing stretches of the season due to bruises, turf toe, concussions, etc he gets flagged as injury prone). A wifebeater probably gets probation in a court of law, at worst a couple games suspension by the NFL. And the wifebeating/child abuse is probably an issue the team has to deal with 1 time, rest of the time they can just pay off the wife keep quiet, so the player doesnt miss games. NFL teams talk to HS and college coaches- they likely all got the same impression that Willis was unreliable.
Willis was a very good player in the one year he played a full season, but the fact remains that he was undependable for multiple seasons. That's the kind of player you spend a 6th or 7th round pick on. 3rd and 4th round picks are where GMs really fill out their teams and find values, and they will rarely waste a pick on an unreliable player (you might see an injury-prone guy go in the 4th if the GM thinks his medical staff can keep the guy healthy). A player with a reputation of not being reliable will generally go in the much later rounds as a 6th or 7th rounder rarely sticks anyways, so if you get production out of them it's a lucky break.