So we're left with look at what happens when you take all the existing cultures in eve, smash them together, and instill a survivalist attitude in them.
It probably wouldn't be quite as clear how they'd end up then one would think, remember what Simon said, look at the Afro-Caribbean groups, their culture is entirely unique, and while the roots can be seen, they've grown into something rather different then anything we've seen before.
And yes, Nihilism, and a defeatist attitude are probably fairly common within certain circles, I think there is another thing to take into account. Hope. The people that make up the Cartel have a home, they have people who see them as human beings, possibly for the first time in their lives. Life in the cartel is likely to be hard, and rough, a sort of frontier life. But that in mind, the people who live it still are very likely to love it, and find it rewarding. There would be this idea that, no one cares who I am, who I was, or what I've done. They've likely had just as many problems as me, and they accept me, no questions asked, and I accept them, no questions asked.
I've always sort of imagined it as an insult in the cartel to pry into someone's past, as its a violation of that unspoken trust that the entire cartel is built upon. The cartel doesn't see race, doesn't see past deeds, they see people.
That's a very, very powerful bonding agent, easily strong enough to overcome the bonds of the previous cultures of these people, and instill in them a disrespect for humanity outside the cartel to warrant the gleeful violations of human rights that cartel indulges in.