I think that word "approve" is not appropriate here but English is not my first language, sorry.
But it seems that you are saying :
Manly = having qualities traditionally associated with a man: strong, virile (per dictionary).
Why do men need to be manly? To be strong to stand against. And aggression is a natural response to defend if threatened.
And this is basically a philosophical endpoint like:
1) basic nature of human beings is fear and hate. The war of all against all 2) basic nature of human beings is cooperation.
Here, I am not protecting stoicism, although from mine shallow understanding, I consider tht stoicism has a nice approach to dealing with aggressive. Overcome basic nature, consider and think how to act.