This is kind of the tl;dr 30-second elevator version of it.
Hegel's Dialectic is at its simplest the belief in a positive idea (the thesis), a competing negative or contradictory idea (the antithesis), and the end result, a new concept that nullifies and replaces both the thesis and antithesis, the synthesis.
Social Marxists, cultural anthropologists, and other leftist thinkers have loved to rely on the Hegelian dialectic to attack Western thought for many years. Edward Said (a literature professor) wrote the famous book "Orientalism" that basically says everything that Westerners believe about the Middle East is pure fantasy, wish fulfillment, the Other; that which the West is not. The West is civilized, therefore the East is savage. Western women are chaste and virtuous, therefore Eastern women are sultry whores (harem fantasy). Western men are honorable, Eastern men are untrustworthy, etc. Said, incidentally, just built his book on the prior work of everyone's famous pedophile, Foucault.
Ok, getting to the point.
Today, why do leftists of all stripes love drag queen toddler time? Why do they love kids burlesque shows? To reference a post from today, why do leftists NPCs love cities and hate suburbs.
Thesis. Antithesis.
The left today is defined entirely by what the right is NOT. To be more accurate, the left today defines itself in opposition to their perverse imaginary view of what the right is.
The left believes the right is Christian, therefore the left exults in atheism, satanism, Islam, etc--anything that is NOT Christian.
The left believes the right is ignorant rural and suburban dwellers, therefore the left is modern and urban--anything that is NOT rural.
The left believes that the right requires strict gender roles and rules, therefore the left wants to tear down the very concept of gender.
The left believes that the right wants to kill all gay people, therefore the left wants to groom more children to be gay.
Edit to add: The left believes the right is irredeemably racist and white, therefore the left exults and honors anyone non-white over anyone white.
Edit to add: The left believes the right is male-dominated and patriarchal, therefore the left attacks anything masculine and praises the feminine.
Some of these points are a bit (but only a bit) exaggerated, but the point is that the modern left is an entirely intellectually bankrupt movement. It is a negative. It can only define itself as the opposite of the right.
I agree with your description of Hegelian synthesis, but I think one thing you forgot to point out is that the hard-left is skipping the final "synthesis" step in all your examples. In fact their moral system remains just as dualistic as the old religion it replaced.
Take for example their favorite morality play: "Love vs Hate," which they installed in place of "Good vs Evil."
Sure, some things like traditional family values and teaching toddlers about sex toys got shuffled to the opposite side, but it's fundamentally the same structure. They just sort everything into love or hate, nothing "synthetic" about it.
On this topic I always go back to this uncannily prophetic scene from Donnie Darko (2001). It's such a bullseye, I can hardly believe it.
Obviously the analogy I'm making here is teacher as the looming blight of dualistic Libstianity and recalcitrant student as Hegel arguing for more nuanced (synthetic) reasoning.
The only slight miss was contraposing "Fear" instead of "Hate" against "Love." But then again, Libstians never miss an opportunity to label someone a "-phobe," so there certainly is still the projection of fear there.
Really great movie if you haven't seen it. It was edgy and leftist in its day, but I'm sure many would call it "far-right propaganda" now.