Is OTHER wrong in the post ? POST : I’m going to preface this by saying it’s not something I’ve done yet, but something I am considering doing.

I met this fellow a few years ago. I’m going to call him Dave. Dave was a friend of a friend but eventually become a close enough friend of mine. I got a girlfriend. She cheated on me with him, and I found that out after I broke up with her for unrelated reasons. A few months later, he falsely told multiple people that i had been lying about something relatively major, that could have destroyed my friendships with them, but thankfully did not. 

January of last year, I found out that this man, a 19 year old, had been describing sexual acts and saying sexual things to a 14 year old girl and a 15 year old girl. He also befriended a very emotional person with the intention of manipulating them for sex. 

I told Dave’s two friends, two more underage girls, about this, and they stopped talking to him as well. I told Dave to stop hanging out with us, to stop going to our usual hang out spots, and to delete his social media’s. He agreed. 

Dave now has a girlfriend. Dave now goes back to our usual hangout areas. I have intentions of telling Dave’s girlfriend about his incredibly questionable activities.

AITA? Or should I let it be? 