Lol why didn't you outright directly ask him to remove his excess clients. You never should use administrative tools unless its absolutely nessarry
I would say "stop," and if they didn't, I'd ban them
I'm not against giving people a chance to quit what they're doing, but I'm not gonna keep giving him chances and telling to stop. I certainly wouldn't ask him to stop, not in a genuine way at least, like I might say "can you stop?" but we all know that's not really a question