I saw it as escalating the logic of the situation - he was in for bank robbery, not just jacking off, unless he killed the other guy.

I found it a kind of in-joke for the part of the audience that knows about kashrut, and given how carefully the show uses Jewish imagery and ritual, I think that was deliberate. It's a figment of religious observance that he wouldn't care about consciously, but also a reminder of Raquel (who he may have heard about it…

No one's mentioned Little Big Horn yet, so I will.