Just guessing, but it seems like most people would consider this to be reason to walk away. Then again, as others have pointed out, one does not need to be a drug user to be an asshole.
I don't usually ask about drug use, but if I did I would probably NOT ask "are you a drug user?" I'd probably ask whether they get into PNP.
Are you sure he wasn't being sarcastic?
Since we are on the topic of how and what to ask massage therapists, I'd avoid asking "May I fellate your penis during the massage" and "Will your massage technique cause me to orgasm and ejaculate at the end if the session."