You, as a father, should teach your son how to be strong for himself and how to deal with difficult situations. One thing is to also teach your son not to be afraid and sometimes when to be afraid. Not only this, but, since being afraid is unavoidable, teach your son how to cope with it. Teach your son not to fall prey to provocations and what to do with the aggressor. Also, teach your son to also be kind, and to physically react only when there is no other option.