but at the same time, i can't argue when people say "it's not our problem".
Cause literally, it's not.
If the couple that lived next door... let's say, a big butch chick and her meth head commonlaw hubby... let's say they liked to fight. One day, it's in the yard. They're beating the heck out of each other. You call the cops, but we all know they take an hour to arrive. Suddenly, the wife is clubbing him. He's all sorts of fcked up. You're watching from your porch. Do you get involved? Well, it's not your problem . He's a meth head, she'll end up in jail for killing him. Society is better, and you have no legal obligation to do anything. It's the cops job, and they're not showing up yet.
Still, you get involved, don't you? Maybe she kills him and you feel bad. Maybe she kills him, puts body in trunk and disappears it, and now you have a murderer (one who knows you witnessed it) living right next door. How long until this murdererous neighbor (not your problem) is suddenly sneaking in to stab you in your sleep?
Shit, look at this completely preventable mess. All because people didn't stop a minor problem when they could.
You're 100% right if you say not our problem, we're broke, let them kill each other, etc. But it's one of those tough situations in this world...you have to kill/subdue/control a monster while it's small. Let it kill other monsters and it consolidates power, commiting major atrocities along the way.