You are too personal. When you come here for help, you should be ready to hear some different opinions, and really no need to argue back.
In my opinion, you are too sensitive. did you hu*****and cause any hurting to your son? if just a slap, not very hard, such as the marks of 5 fingers, then it is more like a culture for kid education.
If you feel your hu*****and really wrong, then talk with him. If you really feel it were a criminal, also talk with him first. Even he were right, it is an issue in this country and let him undersdand and avoid.