Maybe if they had crimes on their record they wouldn't pass the background checks
It's even deeper than that. We don't want to blame any more. Too afraid of hurting someone's feelings. So we let things slide. And then more things slide. Until it's out of control. Which is getting closer.
Laws and such were passed to protect the people. Now, we've gone so far overboard that we're allowing the lawbreaking of a few to affect many many people in the name of considering every whim and whistle of each individual. What's been lost is that to protect the good of the majority, lawbreakers must be punished harshly.
I think it was Blackstone who talked about the whole of the community, and how the needs of the individual must be sacrificed at times to protect the whole, the community.
People aren't going to be good just because you ask them to. Laws must be passed and enforced strongly for the good of the whole. Crime will slowly dwindle if criminals are punished swiftly and harshly. That's the only way that's ever worked.