This is not just modern age, this is how it has been for as long as our knowledge reach back. Women are less prone to violence than men.
Some say testosterone makes men more aggressive, but the problem is that the difference in aggressive behavior can be observed before sexual hormones kick in.
One being male competition for reproduction, and the other social.
Problem is IMO, that it doesn’t swing with behavioral studies of children, that to me seem to exclude both as the fundamental course for higher male aggression and tendency towards violence.
Seems to me it goes deeper, yes we do have competition for reproduction, but so do women, and women can be quite competitive and aggressive about it too, but generally in a less violent way.
A third more likely possibility IMO, is that in a society where mankind consisted of small nomadic groups, the men had a role of protecting the group, while women protected the children.
This role for the male, needs the male to be less prone to fear of consequences of violence, giving the ability to confront danger, where women protecting the children were probably more prone to evade danger.
So yes you could say it’s based on a social role, but that role is not just learned, it’s a genetically encoded social role, that is then reinforced by social structure and hormones. Obviously women have the ability to take the role if needed, because we are sentient beings with ability to learn traits.
Now there is a curiosity in that women have actually become relatively MORE prone to violence for the past 50 years. And the above hypothesis does not explain that.
As I see it, there must be new factors playing a role that did not exist previously. I suspect it could be an increase of man made hormone like chemicals in the environment, that influence our behavior.