I'm sorry that was a bit long, but if anyone has had any similar experiences (I'm sure most seasoned instructors will), I'd love to hear what happened and how you advised the student. I don't know if this fellow will stick with Aikido long-term, but I can see him coming back in the coming weeks at least, so it would be interesting to hear any similar stories.
This sounds like a repeat of the question in this forum a few days ago by a young Lithonian who was being bullied. If your kid wants to learn how to fight back against bullies with a quick learning curve, send him to the local boxing gym. Aikido is simply the wrong thing to learn for him. Once again, another victim of the false propaganda surrounding Aikido.