"I have limited time to RP so I only play against one player's version of X" =/= "Toes have been stepped on because someone asked me to play against their version of X".

The first is understandable and common and the second is a sign that someone could potentially be overinvested. If a player gets offended or upset over a politely worded request for a PSL or meme thread, that's a red flag in my book. Not enough to label them a psycho, but I would be wary.