@KageLycan
Translations are hardly ever 1:1 kind of thing.
Like, one thing is to translate, say, "apple". It's a physical fruit, pass it around by two people who speak different languages and sure, you get a 1:1 translation.
Now, when you get to culture shit, stuff get's muddled. What can be heavily insulting in one language might not translate well into a 1:1 scheme. For exemple, in brazillian portuguese, you could call a cheating man a "Dog" as a slang. That, naturally, does not translate 1:1 into english, so one could forego the cultural context into "cheater".
So yeah, translating is not a simple thing, and one could argue that preserving the narrative is more important than being a 100% loyal to a 1:1 translation (there's a reason most companies that translate stuff don't try to keep to the 1:1 proportion).
Other people have gone more into the detail of this particular translation, and I'm just explaning how translating stuff works, all that said.
"derogatory labels about mental disability is pretty rare" is not a reason to bash this.