I don't think it's really an issue of passion. Rather, it is an issue of demographics: almost everybody is affected or at least mildly interested in politics; only smaller subsets of the population are interested in Haskell/Erlang/complexity/aglorithms...etc. Frankly, I bet some people are as "passionate" (for a loose definition of "passionate") about, say, functional programming as others are about politics; there are just more people with at least a casual interest in the latter than the former.

Also, as HN gets more readers, it becomes more diverse. I've seen doctors, medical students, lawyers...etc post. It's no surprise somebody like that is going to skip a post about using abstract mathematics to model programming or about optimizing lunch at your startup; they are probably gravitating towards the political articles. On the other hand, just being interested in start-ups and CS does not preclude looking at politics.

So really, I think this is a function of diversity: in a purely democratic system--everybody has an equal vote--less specialized things really have an advantage. This is why I don't bother reading the newspaper or front page of reddit, but still enjoy /r/haskell.

I'm sure there are also plenty of confounding variables; I just think it's more broad appeal than passion. (Seriously, have you read the responses to people's blindly disparaging functional programming? At least as passionate as most political posts ;).)