It wasn't that long ago that men killed and went to war against other men for violating their wives, sisters, mothers, or any other family member or close one. History is replete with stories of the chivalrous man coming to the aide and defense of a woman.
Frankly, I don't think you can lay the blame entirely on men. Most men I know would take action if someone close to them were sexually assaulted, sometimes action that would land them in jail. If my wife or my daughter, or my granddaughter came to me about something like that there is no way I could let it go. The perpetrator would regret the day he laid a hand on them. I am mystified that the man, or men, who are related to or very close to these women would not take action. You have to wonder what kind of men they are, or you have to wonder if they knew it happened at all.
I agree with you in large part. Though standing up for one's wives, sisters, mothers when they are sexually assaulted is not enough.
We ought to stand up for and honor ALL women in ALL circumstances. This means speaking up and saying that it's wrong when a friend makes lewd gestures towards a woman at a bar, for example.
While the blame isn't entirely on men, we certainly have a lot of responsibility for the situation and must answer to that.