To be concerned about friendship with class bully

[UpTooLateonaSchoolNight]

My DS is 8, just started Yr3. He’s very respectful, kind and follows the rules. We’ve had a chat tonight about his class and he told me that he chooses to be friends with two children in his class because they don’t have any other friends. This is very admirable. I know both children, one has “annoying habits” - that’s fine, no reason not to be friends. The other is becoming the class bully by all accounts. My son has been close to this child since YrR, so I understand the friendship, but it does concern me. I asked him to think about why others may not like this child, and how he might help, but also to be careful. However, I felt mean saying this to him. I’m not sure I’ve handled it in the right way? WWYD?

YABU - they are still young children and it’s good to be friendly
YANBU - I would also be concerned about friendship with troublemaker/class bully

I think it's ok to be concerned and keep an eye on it. Have a chat with him and ask him if his friend has been mean to others? Does he get into trouble with the teacher? And give him some strategies as to what to do if he sees bullying/mean behaviour in general.

How is one the class bully when nobody likes them? What does "by all accounts" mean? They're 8 years old

Because these kids have been in pre-school together since they were 4. Kids start off as friends, but if one child starts being mean to other children, then they don’t want to be friends with that child anymore and avoid them. “By all accounts” means that same name keeps coming up when discussing things that have happened at school. I understand these children are 8, that’s why I’m asking advice as to whether I should be concerned. I don’t want my child to be associated with a bully, when he is trying to be the complete opposite. Maybe he is doing the right thing - I’m willing to be told I’m wrong.