Because misinformation is misinformation, and i'm not a fan of sitting by and letting it drop, whether it's happening to me, my colleagues, or even companies i don't particularly like personally, but happen to know facts about.
Particularly when this is used as the lead-in and part of a strategy of supporting an argument.
In fact, i'll point out that RMS is actually very good about this stuff himself. If his position is based on factually incorrect info, and you correct it, he will often immediately change his position.
You spend a lot of time negating dmm's comments about Apple, when most of his post was about pools of power controlling or attempting to control a given bit of software. Granted, Apple spends a bit of time doing this very thing quite frequently and most people seem cool with it (because it's so easy!), so I'm curious why you are so set on defending it?