I named my dog Retarded. So if anyone says: "Are you fucking Retarded?" i can reply with a yes.
Are you ok with being called this?
Yes, of course, why not. If a retarded person can become a pet, who's to say that a retarded person cannot be a useful pet.
I doubt people with mental disabilities want to be referred to at retarded.  I can help you if you wish to learn about some things disabled people prefer to be called if you like.