Discrimination

I don't too often get upset over this but I'm tired of the disrespect I receive from looking really young. I went by a small club/ music lounge with my boyfriend & his friend. The age to get in was 18 but We were planning on staying outside in the parking lot & the door man let my boyfriend & his friend by to the other side of the lot. The door man stopped me & asked for my ID.  My boyfriend & his friend didn't notice I wasn't behind them because it was a lot of people.the door man told me to leave the parking lot because I wasn't 21 . He threatened to call the police & my boyfriend had to come over to help me get out of "trouble" . How can my age or how young I look be referred to as trouble ? I felt so embarrassed in front of all those people ... Humiliated actually.  Then on top of that he asked if my boyfriend & my friend were a couple. I just felt really angry.