Is this appropriate?

Ok so I have a question. I've had people tell me that it's perfectly normal for a guy who has a girlfriend to stare at a female while she's bent over. I wanted to ask your opinion do you think that's appropriate and a valid excuse? I have a class with a guy its in a dance studio and there is a mirror in the class that shows our reflection. I came into class and this guy was already standing around in a circle with a group of people talking to them. So I came in put my backpack down and I wasn't even thinking about the mirror behind me and I bend down and open my backpack looking for my notebook to take notes and once I found it and raised up I saw that this guy had been standing there the whole time staring at me while I was bent over and his was just standing there with this big open smile on his face just staring at me and wouldn't look away. Even when I caught him staring he wouldn't look away, so I looked away because it just felt awkward. This guy has a girlfriend and I'm trying to figure out is that appropriate for him to be staring at me like that. This isn't the first time that he has been staring at me. Each time he stares when I catch him he doesn't look away and just keep staring. Other females in the class have noticed it too and they be looking at him wondering why is she staring at me like that. Is this appropriate? Please only respectful honest answers. Be kind when replying or I will block those who have the need to be nasty and rude. Thank you for reading my question :)

Is this appropriate?
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