That's half the problem, they don't contain themselves to those communities. If they find the faintest way to jam Linux into an active conversation, they'll do it regardless of the community.
I think you're missing the idea a little. Yeah its not the biggest problem, but these guys don't just suggest Linux, the people that just say they prefer it in context and to look into it are fine.
Its the high schoolers and early cs major - types who heard someone else suggest it, and now they've made it their entire personality and are physically incapable of refraining from going off about how much better Linux is than windows, while not particularly understanding what they're even doing.
Example: When I started my programming degree there was one high school kid taking the courses, ANY time someone had an error with their IDE he would go off about how Linux doesn't have any issues.
And then when the group went to go play games together, he'd attach himself to the party and spend like 20+ minutes crying about how the game didn't run well cause devs only dev for windows while he struggled with his wine setup.
Ooo look at this rugged, world weary badass. You want to improve something? TOUGH. Life isn't fair kid! Just grit your teeth and take it like the rest of us do-nothing insufferable fuckheads do!
More like that people are free to be annoying and there's much much you can do about it. If you're not mainstream enough, most memes are just junk noise.