The most concise definition I've heard of leftism a comment from Erik von Kuehnelt-Leddihn, in his magnum opus, Leftism Revisited: it's about "the murder of the Father."
I picked this up from the Elusive Wapitii.
“Why are we here today?” she asked.
“To make revolution,” they answered.
“What kind of revolution?” she replied.
“The Cultural Revolution,” they chanted.
“And how do we make Cultural Revolution?” she demanded.
“By destroying the American family!” they answered.
“How do we destroy the family?” she came back.
“By destroying the American Patriarch,” they cried exuberantly.
“And how do we destroy the American Patriarch?” she replied.
“By taking away his power!”
“How do we do that?”
“By destroying monogamy!” they shouted.
“How can we destroy monogamy?”
Their answer left me dumbstruck, breathless, disbelieving my ears. Was I on planet earth? Who were these people?
“By promoting promiscuity, eroticism, prostitution and homosexuality!” they resounded.
The Manosphere is a response to feminism - but not all of it. That's why it's such a mishmash. In some ways it's just as leftist as feminism, e.g., the promotion of the PUA and MGTOW lifestyles. Each of those destroys monogamy and patriarchy just as surely as feminism, which is leftist.
Ironic, isn't it?
There is an old saying, "As women go, so do men, and so does society.
Let's put it this way: women were the first to go Women Going Their Own Way, with the emphasis on career over marriage, and were the first to become their version of the PUA lifestyle with the promotion of promiscuity, and now, Slutwalks.
It's why I've pointed out, among other reasons, why there is nothing new in the Manosphere. Because in many ways it's just men following women - to each's destruction, and therefore, of course, society's.
That's what happens with the promotion of Hedonism - which, by the way, was thoroughly debunked by the Greeks thousands of years ago. Not to mention the Bible.
It's why I've pointed out that people like Roosh and Krauser and Roissy are frauds living lives that will lead to their destruction - the lies, the promiscuity, the whoring (and don't think they don't) - the hedonism that leads straight to boredom and ennui and hopelessness.
Which is the end result of being a leftist and not even knowing it.