I have autism, tourettes, ADHD, dyslexia, clinical depression, and severe anxiety. I've been to three psychiatrists for all of this.
You wanna know what I though of when he said that? I giggled. I took it as word play and thought it was funny. I'm also the same person who does not care about the "R" word. I'll use retarded alot, and it pisses me off when people say "don't say that!" I say "fuck off, it's what I got." I never call an individual "retarded" but I do call actions and objects the latter. If there's one thing I've learned through nothing but experience: If you can't laugh at yourself, you can't help yourself.
Another example, I dated a girl who had been previously raped. Seeing R34 images would put her into a PTSD episode. However, when having a conversation with someone, she could play certain things off as a joke, or joke about sex stuff in general. She learned joking about it helped her to cope.
I'm gonna be real here. If you don't have a mental disability, shut the fuck up. Hardly anyone with mental disabilities takes offense to the stuff that people who white knight us do.