I suspect it's because programming is an intense meritocracy, but a meritocracy governed by the intense subjectiveness of how smart your peers think you are rather than some more objective criterion like published papers or citations.
Therefore, to some programmers, if someone else is likely to do something more brilliant than you, it's motivating to stop them. Especially so, since if you are successful in stopping them, your own perceived merit goes up as the smarter dog in the room.
This game is reinforced by the game of karma on many programmer discussion sites. I have to admit, I succomb, as I want my karma to cross 200 so I can downvote. It's a stupid goal, but my ego is prone to it.
P.S. Please note that science is also prone to this behaviour, and programming and science have the same solution to the problem: actually building a verifiable { experiment / correct theorem / more efficient algorithm }.
cf. Science in Action by Bruno Latour (1987), which I tried to summarize on http://www.usemod.com/cgi-bin/mb.pl?SocialConstructionOfScie...