Yeah. It's a tricky one. I am of the mind that using it on oneself does not give one a pass to use a slur.
For example, when you call yourself a "kike", you are not being bigoted only to yourself, but to all Jews. It's still antisemitic, no matter who says it and no matter who it's said to.
Yeah, it's complicated. The most obvious example here would be usage of the n-word. "Arguably" that is somewhat different in that, like a term such as "queer", it has been re-appropriated. But again, it all comes down to who you ask--a lot of Black people detest the n-word, no matter who is using it.
With re-appropriation, or
attempted re-appropriation, there's always a reactionary element. With a term like "kike" and such things related, right down to Holocaust jokes, it's partly the OTT zealotry, especially over the past decade or so, of groups like the ADL. And they've gotten
real bad: from declaring anti-Zionism to be equivalent to antisemitism to--seriously!--declaring the keffiyeh to be antisemitic! The former is one thing (and it's just
wrong), but the latter? That reads like a bad joke, but that actually happened.
At the same time, I actually generally am inclined to agree here with regards to the specifics: "kike" is unacceptable, even if referring to oneself. I think my usage of such, a couple of pages back, would be more an example of, perhaps, "poking the bear" or something like that--maybe being pedantic in the least effective imagineable way!
But even "spastic" is complicated. In the US and Canada it was always rather vague in terms of meaning, but even so far as particular qualities or medical phenomena go, it alluded to any number of things--see 0:55 in the DEVO video below. That guy's name is Spaz Attack (presumably not his given name, but rather a chosen one). Whereas in the UK, it was mostly used as a slur against persons with cerebral palsy. IOW worlds apart, as far as implications go.