I don't see how you saved the child from anything. You punched him in the face. If you need gratitude to justify your own "good deeds," then you, like the child, might not understand the nature of good deeds (which should be valuable in and of themselves). If your intentions were to protect him, you're not the best at connecting results with methods.
But I would level such criticism at you regardless of your response to the above comments. I don't see why you think beating up eight year olds will teach them anything about values. Somehow you've come to believe that your violent "teaching methods" are effective despite all available evidence to the contrary. Perhaps some corporal punishment is acceptable- maybe a spank or something from a parent (not a debate I wish to enter)- but a punch in the face? Do you think he respects others now? Why would the knowledge that some people are unable to control their rage instill respect?
Please, all this "teaching respect" BS is only a means to justify your own inappropriate response. You hit a child. Don't fool yourself with bogus explanations; you did it because you couldn't control yourself, and to satisfy your own rage, not because you were doing the child a favor (by teaching him something).