My SO's Facebook "friends" bother me so much

So my husband and I graduated from high school just a few years ago so Facebook is sti full of those high school friends. That being said, he was a cheerleader and had several girl friends (not girlfriends,gfs) and is friends with many of them on fb. Every time I post a pic of us or just of me, like my bump pics, and I tag him in them I get an overwhelming amount of little girls he went to school with liking everything and commenting. This bothers me. A lot. They aren't exactly modest girls either. Some are just straight up trashy and it bothers me that they still keep up with my husband. Am I being petty? How do I explain that I don't like it and how could this be remedied?