Mothers should be involved, even in two parent homes, to show how boys should compete for and defend girls. I have a friend that actually allowed her kids to watch their dad fight for her to show them what's expected. I also know moms that set their sons up to fight each other.
I think small groups of women will encourage the boys to fight, especially if girls their own age are cheering them on. Other boys or men present may mess with their minds too much, at first. Just because a boy is a wimp doesn't mean he won't fight with the right encouragement. If you come down on him too hard he may never fight. It depends on the individual.