<human>: Can you condense the text into a few key points?

My boyfriend's cousin was in a performance of her middle school play, The Little Mermaid. He and the rest of his family went to go see the show last week. He claims that when the girl playing Ariel came out on stage, he had a quote, "split-second" attraction to her, thought her to be "some kind of hot...well, not hot, just attractive" and then promptly started to freak out because he was grossed out as to why he would think that. He spent the rest of the play uncomfortable, and trying to figure out why he even felt that way in the first place. 

After long discussion if him freaking out and me trying to wrap my head around this, he tells me that he has never felt like this towards a younger girl before and he wasn't even sure why he felt attraction to her in the first place, as he was in the back of the auditorium and couldn't really even see what she looked like. He assumes that it had to be a result of her in costume - a body suit under the bikini and tail. However, he says he is still confused because the girl (obviously) didn't have a body (ie, boobs, butt). 

Now he confined this to me, and I'm having a very hard time with this. How could he at almost 21 feel an attraction to a middle school aged girl? I feel disgusted and conflicted and I honestly want to help him through this as well. But how big of a red flag is this? I can't be with someone who I think shows signs of pedophilia...
<bot>: My boyfriend felt attracted to a middle school girl dressed as Ariel from The Little Mermaind, and was immediately disgusted at himself for feeling that way. Now I'm seriously freaking out.