How do you deal with comments about your masculinity or people trying to emasculate you?

I was at the doctor yesterday and he was trying to make conversation. He said he's an open book so if I have any questions about anything just let him know. I said alright and then he got quiet so I decided to ask him how he got into the profession he's in and he replied "Well I'm not sure I want to answer that". I said that's fine and he said "I was a nurse for a couple of years and then I went back to medical school and got my license and now I'm here." He literally looked like he was in pain when he said "I was a nurse". I just laughed and he looked at me like "oh you know what I mean". I don't understand why being a nurse is any less of a job compared to a doctor.