Teacher plays sml for kids in class

I'm a substitute teacher, typically a para in a special ed class, such as today, it was elementary 3-5. A student was trying to pull up the Jeffy song on youtube, I'd only seen maybe one or two videos, and it's been years, but I am a little familiar with it, and know it has some very innapropriate content for kids, which obviously I can't control at home, but in class, I wouldn't allow it. However when I exited out of it, the main teacher got onto me, asking why I think it was innapropriate, because she lets them watch it, and finds it okay. When she asked me, I wasn't sure exactly how to respond, because I didn't know much, and couldn't think of an example at the moment. (However if I remember correctly Jeffy is a mentally disabled character, and a victim of SA, but I didn't want to say without being sure.) What do you guys think of this?