The main reason, I think, for any amount of PC "elitism" is that there have been many people who have said things like "PC gaming is dying", "PC gaming will die", and that there have been some signs of PC game dying out. It's, at least in part, a drastic, worried response to a potential issue.
Those of us that game exclusively on the PC especially have this issue, because we see the PC as being superior for one reason or other, yet others don't seem to quite understand how it is better - and, more significantly, in the former decade as consoles were getting better developers seemed to vastly prefer consoles and those platforms swelled suddenly in importance.
Knowing why developers prefer those consoles, seeing that sudden swell that looked like it very much would simply overtake and suffocate the PC, and similar developments like games being released exclusively on consoles or earlier on consoles (I believe it happened only a few times, though, and I may be mis-remembering entirely) combined with a love for the PC for whatever (mostly the mouse, keyboard, and general versatility of it, for the record) easily spelled disaster.
I do think the PC is the best platform, hands down, but I'd never call it the master race, or suggest the consoles stop existing. Consoles are good for their own reasons. I just don't want PC gaming to die out to any degree.