Am I wrong to want my ex to stop hanging out with a certain guy?
Why do you want your ex to stop hanging out with a certain guy?
Because I don't like that guy and think he's mean.
It's fine to not like this guy, but you shouldn't tell your ex that you don't want them to hang around him. What your ex does isn't your business, so I think you should stay out of it.
You are wrong, he hurt me and I don't want what happened to me to happen to my ex.
It's important to realize that your experience with the guy is going to be different from your friend's experience. Instead of trying to come between the both of them, you should allow your ex to learn who the guy is on their own.