Subtoot, CW discourse (serious this time)
It's one thing to bitch about someone asking you to CW the word "stupid" as ableism. It's another to bitch about someone else just doing that thing without asking anyone else to do the same. Everyone has their own standards on what they feel is CW-worthy. If you think it's...stupid...to CW something like that, that doesn't matter. They felt it warranted it and that's all that matters.
Subtoot, CW discourse (serious this time), trans slur
This isn't to say there aren't things that shouldn't be CW'd, regardless of how you feel about it. You may not feel stupid deserves a CW, and that's fine. But regardless of how you feel about a slur like "tranny", it needs a CW. Same with all manner of things. NSFW stuff, for instance. Or politics (generally). Violence. Stuff that might generally be upsetting, you know?