Your use of the word "dominates" is disingenuous. Let's imagine:
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There exists a country in which 95% of all leadership in government and industry is male. There are a few women here and there, but for the most part, it's all men at the top. And at the top, people are pretty protected. They can generally get away with whatever they want, as is often the case.
This country has gender roles. Legally enforced gender roles. Women are viewed as more fragile caregivers. Men are viewed as sturdier providers. People at the top of society are pretty insulated, but for everyone else, these gender roles are a fact of life.
For a given crime, men are held to higher standards, and they are subjected to more brutal punishments. Men overwhelmingly find themselves in dangerous, thankless jobs.
Young men tend to work menial jobs, while young women tend to attend university.
Men do not live as long in this society. An overwhelming amount of public money and attention is spent on issues that primarily affect women.
And when a woman is perceived to be slighted, men and women are expected (and socially rewarded) for rushing to her aid. Men, being sturdier, are expected to fend for themselves.
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Every well-off feminist man I've encountered would say that men in that society are not victims of sexism—they are simply victims of patriarchy.
Why on Earth would one call that system "patriarchy"? Aside from the top of society, men have it worse in this society. Men have it much worse. Why lump the men at the top in with the men at the bottom just because they all have penises?
Please realize that men can be sexist toward other men. Men can actively oppress other men on the basis of their gender. Men love competing with other men. Men love one-upping other men. Men love protecting women from those other, less civilized men. In short: Many men love oppressing other men.
For poorer, underprivileged men, it's incredibly marginalizing to hear a hyper-privileged man display his plumage and say it's alright to hate males, because males "dominate" society.
Unfortunately, repeating that mantra costs that hyper-privileged man nothing, yet it can potentially increase his social standing among other hyper-privileged men. So why wouldn't he?