Would you ask for context if the request were for a ban on racism, transphobia, etc?

Not transphobia. But racism, like ageism and other -isms, does need context. For instance, you can make the claim that "cracker" is a racist term. Strictly speaking, I agree with that; I just don't mind that form of racism (not that it matters, but I am white). This is why in general I try to use terms like white supremacy, patriarchy, etc. Those things have specific, systemic harms.

Ageism is a harder one to pin down. For instance, I saw a crossword clue a while back where the answer was "ageism," the clue was "A senator might experience it" (or something similar). Well, sure. Being old clearly helps you gain the immense power of being a senator.

I also think "ok boomer" isn't a slur the same way your other examples are. Being a boomer brings some pretty decent benefits, not to the same extent but in much the same way being white brings a lot of benefit.

But I'm not denying that ageism exists & brings specific harms in some contexts. I just don't think there's as easy a blanket "this is ageist, take it down" as there is for patriarchy et al.