I simply asked if he thought it was professional to comment on a woman's (whom he referred to as a 'girl') appearance with her. I work with young people and have never commented on their attractiveness because I believe it is not relevant to my job and inappropriate to do so.

"Live a little. Have a life." Whatever, if you think that commenting on a young woman''s appearance, while you are working in a professional capacity, adds to your life, have at it.

I think you might get a warning from HR for that.