"Sorry, we can't be friends anymore, you use bad software." Look, I guess I kind of get what you're saying, but unless you're Stallman this kind of lifestyle just isn't viable. Real people just want to use the thing that's easy to set up, good enough for their uses, and most importantly already popular. Network effects are a real showstopper for those of us who'd like to move to FOSS alternatives, and when the options are to either use the popular thing and communicate with our friends, or insist on the FOSS thing and isolate ourselves, it takes more zealotry than most of us can muster to commit to the latter.