rude or ....?

Am
My son is 4 years old and he is getting to the age where he is curious about other people's bodies. Since his sister is 9 months old and he has another sister on the way, I decided to fully 'wean' him. I used to take baths and showers with him and I've completely stopped it. I've never allowed him and his sister to take baths together either. Even though that's something my parents allowed. His father takes care of all of the boy stuff. Well my cousin is 17 and she was getting dressed for work, so I went in the room and told him to get out. He is a boy and she is a girl, and it's not appropriate. My aunt always has something to say and says " oh it's fine, he is only four he doesn't know better" and I say no he needs to get out. She is one of those people where is you don't do as she says she calls you a bitch and rude no matter what the circumstances. She argues further and says I'm being unfair because he doesn't get to see my cousin as much since she works now. I said, "no, he is a boy and she is a girl. He doesn't need to be in the room anymore, he is getting too old" and she tells my son "it's okay you can stay in here" IN FRONT ON MY FACE. I take a VERY deep breath and grab my sons hand and ask "what are you?" He says boy. I point to my cousin "what is she?" He says a girl. I point to the door and he walks out and waits patiently. My family does that ALL THE TIME. And it's too the point where I don't even wanna go there anymore. Was I rude or no? Because I don't think so.