Is it too controlling to forbid my son from playing with this kid, and if it's not, how do I go about that?

I'm sorry for the novel I wrote. I have been having some severe trouble with a kid that my son is friends with, and I need some advice on helping my son “break up” with him.​My son is 9 years old, and has had this friend “Sam” since last school year. They became very close over the summer. My first red flag about this kid was that every time he was around, my son’s behavior changed to include things he rarely ever did before. (Not that my son is an angel, by any means. He has ADHD and is often having outbursts of noises or words, and struggles with being able to stay on task and do what we ask of him. But at his heart, he is a good kid, who generally listens to what we ask and knows and follows our rules.) Whenever this kid was at our house, no amount of correcting our son’s behavior would work, so I had to send Sam home countless times because my son would just promise to listen to the rules, and then continue to break them. I didn’t like that when Sam was around, my son became defiant and rude. (I also saw, when Sam was at his home, his mother had no control over him. She would tell him to stop doing something, he’d continue right in front of her, and she’d just ignore it.)​As the weather got warmer, I started letting him ride his bike around town with Sam. I was wary, because I was worried about his tendency to be defiant when Sam was around, but considering the small town we live in, there were almost always eyes on them, and I knew other parents would let me know if they saw my kid up to no good. This is around the time that my son started becoming disenchanted with Sam; he said Sam was always trying to ride where my son knew he wasn’t allowed to go, and was trying to get him to do things he wasn’t supposed to do, like trespass on someone’s property to play in someone’s koi pond. He also told me that Sam liked to ride his bike around other neighborhood kids and try to instigate fights, or at least was saying rude things to them, and was swearing a lot. He would just say goodbye and ride back home whenever Sam would push him too far. I was proud of him for being able to separate himself from situations that made him uncomfortable, or that he knew were wrong, but I was also wary of continuing to allow him to be friends with this kid after I learned of this behavior. But, coming from a very strict, very controlling household, my “parental control” meter is all out of whack, and I didn’t know if it would be too controlling of me to stop this friendship. So I warily decided to step back and monitor, and trust him to make good choices.​Now, however, after several months and various things this kid has done, I am pretty much done, and thankfully so is my son. The first "final straw" incident was when they almost got the cops called on them because Sam was mouthing off to another neighborhood boy, and that boy’s uncle came over and started yelling at Sam. That boy’s mom messaged me saying everything was all on Sam, my son hadn’t done anything, and looked mortified that he was even near Sam when this happened. Sam tried to tell me that he hadn’t done anything wrong, that this guy just came up and started yelling at them, but later in private my son told me that the other boy’s mom was right, and Sam had been teasing a kid and that kid’s uncle had enough. My son stated away from him for a few days but then I guess got bored, and wanted to hang out again. He invited a bunch of kids to our yard to play (including Sam), and shortly after my son came inside saying “Sam is throwing poop at us.” Sure enough, my son’s shirt had poop all over it. Sam was taking my dog’s poo piles from the yard, scooping them up with a DRINKING CUP I leant him, and throwing it at kids. (He claimed he thought it was mud.) I sent him home and texted his mom to tell her why. She didn’t seem to believe me, and said that “We will just keep him around our house from now on.” Except shortly after this, the boys went to another house to play, and Sam was riding by, giving the kids the middle finger, calling them pussies, and saying “So-and-so is a way better friend than you guys ever were anyway!”​The long and the short of this is, I no longer think I’m being controlling by telling my son that he can’t hang out with this kid anymore (though I did type this novel out because I want people to be honest if they think I am), and I am going to tell him and his mom he can’t come around anymore. I am worried that he will try to bully my son and his friends after I tell him this, but that we have a plan for. But my real question is, how in the heck do I go about ‘breaking up’ with this kid on behalf of my son? Do I just say “I’m sorry, but you can’t come around here anymore. Leave my son alone, and if you guys see each other out and about just ignore each other”? Should I specify some behaviors that caused me to do this, so he can maybe reflect? Should I tell his mom that I’m telling her son to stay away, and if so, how do I go about that? Do I tell her why? I have talked with a few other neighborhood moms and none of them want their kids around Sam either, but none of them really know how to go about this either.​ via /r/Parenting https://ift.tt/2zMq3CG