It's not a conscious choice. It's subconscious, something emergent from the interaction of many groups. It's not like the career criminal is fleeing with a successful yield from a home invasion and on the way to the pawn shop is thinking: "I want the people living in the homes I invade to have fewer guns, so the odds of me getting shot after I break down the door decrease".

It's more of a hivemind decision. A given home invader is asked about his politics of gun control, and he reaches into his brain for an answer and it goes like this: "I like Democrats because they give me other people's stuff that I didn't earn, and Democrats are anti-gun ownership, so therefore since I'm a democrat, I'm also anti-gun ownership."

The reason for the affiliation is beyond the capacity of the career criminal to understand enough to know that the hivemind is looking out for his own best interests (home invading) even though the career criminal is unaware of the mechanisms that make his life easier.

Examining how this stuff works is incredible, it's like a jet engine and a clock. Evolution, Genetic algorithms, Neural nets track in toward optimalities even though each participant is unaware of how they relate. Humans are like ants. So trying to find the source of the behavior of the colony by examining the contents of the ant, you will find nothing there.