People don't commit crimes because they think it's a fun hobby to get into, they commit crimes because their pushed into a corner and feel they have to.
Who pushed them into a corner, why, and is that not a crime itself?
A lot of crime is situational, but it can't be abuse all the way down. Some people are just bad people. Or make very bad choices, at any rate.
Sure, a single mother stealing food for her kids is sympathetic. How about a person who abuses or rapes one of those kids, or the mother herself? What "material condition" should be addressed there?
If Babylon hadn't started the vigilante force, the refugees would probably have formed one of their own. Or worse, multiple competing gangs.
It's a bad situation sure, and the government is at fault. But the vigilantes? Well, they're a response to the "material conditions" of not having any other law enforcement. It's an ugly solution for an ugly situation, but given that, they seem a decent gang from the little we've seen.
I note the leader is willing to take a lot of outraged interrogation from this new kid... I'd guess that Benika's accent and fluency mark her as obviously a native[1], so he's being cautiously polite in general and maybe taking the opportunity to get some word out, too.
[1] Or maybe they're all talking English badly.