It's not his contributions (or lack thereof, depending on your point of view) to computing that draws the ire. It's the really, really stupid things he says, as if the world were physically constructed of 1's and 0's...

Personally, I find his political views on free software to be interesting only because they illuminate a fascinating personality. Coming from anyone else, they'd be discarded as irrational drivel. But from Stallman, they become an insight into a peculiar and interesting man.