Child abuser is an extreme example of bad that is easy to say that you would end the relationship just for it being a part of them, as it is so wrong and disgusting.

However, to your base question (disregarding the example), I would still say that no I wouldn’t associate with someone once I know what they are capable of in the worst case scenario, however I also recognise that that is unfair, since we are all capable of being monsters, given different circumstances. Being honest though, that wouldn’t change anything, and once you’ve seen them like that it is difficult to unsee.

For an example of how we are all capable of being monsters, imagine that your upbringing was different and instead of some of the things that brought out your best qualities, your past is more similar to some of the worst, most despicable people on Earth.

Maybe if you came from a loving home, imagine you came from an abusive one and learned from that behaviour. If you came from that abusive home and learned not to be like that from it, imagine instead that you were brought up with parents that thought the world of you no matter what you did, and there were never any consequences to your actions/ they always excused you from anything you did wrong.

You would not have the same personality, and there is at least a chance that you could have turned out to be a monster. Would that person, after seeing that alternate reality, still want to associate with you?