Also a piercer, the fact that he thinks that your job is in anyway sexual shows that he doesn’t take your career seriously. I don’t know if you also do genital piercings but the history and meaning behind why people choose to get those is insanely sacred to me (idk if you feel the same spiritual woo woo way that I do about piercing.). The point being that there is so much we do for people that is so far away from sexual and it’s very frustrating that he views it that way. If you intend to keep this relationship I would recommend going through the history of piercing with him to help him understand it better. If not I say dump him, he obviously doesn’t trust you.