How to tell sports coach that my son is leaving?

[cheesecakeandtrifle]

My son (aged 5) has been a member of a sports group for the last 18 months or so.
Never any issues until recently when a new boy joined and started causing endless bother for most of the other boys... Not sure what the situation is with the new boys (whether he's possibly neurodivergent or has special needs) but he's a damn nuisance tbh. Constant name-calling to the other boys, pushing them and generally making a show of himself.
I'm aware that at least 2 other parents have complained to the coach about him.
For the last couple of weeks my son has said he wants to leave the group because of this boy.
My son isn't physically scared of the boy (my son excels at karate and isn't shy about defending himself against bullies if necessary), but he just seems to find the boy draining and a damn nuisance.
He's asked me to tell the coach that he wants to leave, but how can I word my email in a diplomatic way? Obviously the coach is aware of this boy being a nuisance (due to 2 previous complaints), but I don't want to come accross nasty, although I do think it's important to leave the coach know the true reason for my son leaving (instead of making excuses like being too busy/tired etc to attend).
Any idea on how to word the email?

I'd just say x will be leaving the club. He's really not enjoying it any more.

If the coach asks why, tell him.

He's well know in our town, has been in local press quite a bit regarding his karate achievements

Where do you live? Pontypandy?

We lost a child with known additional needs due to the behaviour of another that may or may not have had additional needs. We were willing to work with that child but the parents withdrew them without telling us and we never got the first child back which was a shame all round. We lost two children. Child A left an activity they'd previously enjoyed even though the issue had gone and Child B could have been managed to conti nue the activity and improve their social skills. Child B hadn't been with us long, and it rapidly escalated beyond normal range tit for tat bickering within a couple of weeks.

It is useful for leaders of youth activities to know if there are issues affecting their membership so they can take appropriate action to manage it without kicking anyone out.

No need to mince your words

"Jim, I'm afraid Toby says he wants to leave the group. He has loved his time with you until Sam joined. There's no easy way to say this, but Sam's behaviour and interaction with the group is the reason Toby wants to leave. Is there anything you can do? "

And I have no idea why the other posters are being so bloody mean!

Because it's NOT the karate club he wants to leave. It's another, completely unrelated club to karate. So there's no need to go into great detail about how brilliant her son is at bloody karate. It's irrelevant.