I think it sounds straightforward when you lump all men together into some homogenous group. However, in reality what is the average UK male going to do about the Palestine conflict, or even about the violent male two streets down from him?
I also don't think we can 100% assume things would be better in a matriarchy. Men commit most war crimes because they're in power, and they likely attain power because of their high testosterone, greater physical strength, and greater inclination to work together than women - this pattern of men dominating started centuries ago when warfare was still hand to hand combat and winner takes all without NATO alliances etc.
In a matriarchy we would probably just see the most aggressive women rise to the top and history shows that in the rare instances that women attain power they can be as bad, often worse, than male rulers.
For example, Historians believe that Elizabeth Bathory is very likely the most prolific murderer of females to date, with a body count estimated at 650, most of whom she sadistically tortured to death with hot pliers etc.
Queen Isabella founded the Spanish Inquisition which went on to torture thousands of females, and that's before we get to Bloody Mary killing hundreds of protestants , Wu Zetian murdering many including her own family, Princess Olga of Kiev burning political opponents alive, Irene of Athens having her son deposed and his eyes gouged out, Queen Ranavalona of Madagascar murdering family members to retain power and starving her aunt to death, Elizabeth I persecuting the catholics, Catherine the Great deposing the czar by force, Cleopatra conquering Egypt, and Isabella of France deposing her husband via coup.
There are many more but I think this is enough to illustrate that powerful women can be extremely violent too when given the chance. In some ways we might be worse in power as studies have repeatedly shown that women don't collaborate as well as men and that a man/woman are more likely to work well together than two women (but still not as well as two men).
We also resent working for other women and the studies repeatedly show that women favour male bosses and are less likely to cooperate with a more powerful woman. So a minority of aggressive women ruling the world could well be worse than the violent men and much more volatile for all we know. I mean, even looking at mumsnet will show how much more inclined to squabbling we are than men.