It's derogatory only when used as a negative descriptor of something, as it insinuates that "gay" = substandard or less than good. "Gay", as far as I know, is not a derogatory term. This is VERY different from, for instance, using the term "(N-word)-rigged" to describe a lousy job on a repair. That is because not only does it use a word which decent people do not use, but it also insinuates that the person saying it thinks Black people can't fix something correctly, or some sort of nasty insult aside from the careless use of a hurtful word.
With that said, I'd rather just say that something looks goofy or poorly-thought out, or in the case of a failing repair, I might say "botched". That way, there's no need to think about who one might be insulting with or without meaning to.
I never knew that "Mormon" had any negative connotations, although among my friends of that faith, most say "L.D.S." .
Charles