I don't agree. If computer is something that is dear to him, then I think it is the perfect consequence to unacceptable behavior. At that age, kids should know that hitting is not acceptable, period. Your son understands that hitting is wrong, and as long as he knows the consequences ahead of time, then I think taking away the computer is fair. He is in charge and in control of this happening. No hitting, computer time. Hitting, no computer. I think this would stop that behavior short.
When my dd was little, she used to ask me what the consequence would be if she did x behavior. Then she would decide if doing it was worth the price she would have to pay for it. It usually wasn't!
