I refer specifically to Marxist Communists. These are the types that believe that Capitalist society is controlled by a ruling class of Straight White, Cisgender, Christian Men and that the institutions and social constructs that make it up merely perpetuate this power dynamic by oppressing all those that fall outside of that narrow category. To resist, deconstruct, and dismantle what is viewed as "their" society is, by definition, to dismantle long-standing systems of oppression.
In this worldview, there is no such thing as "truth"; only "power". Truth, morality, objectivity, individualism, gender, etc. are merely social constructs used by the greater powers as a means to "other" those who fall outside of the paradigm. Any interactions between two parties are just power exchanges.
Why are sluts suddenly not bad? Because the very idea of "slut shaming" is an oppressive patriarchal system meant to oppress women's freedom. Fighting against that dismantles yet another "oppressive system".
Why are there "infinite genders"? Well the idea of a gender binary is just an oppressive social construct meant to oppress those of the LGBTQIA+ community. Clearly by dismantling it, we break free of the constraints of the bigotry of the Christian Patriarchy.
You get the idea. The way this happens is by employing, among other things, shaming tactics, bureaucratic capture, and witch hunts. The adherents to this ideology have a very specific dogma that they follow, since they're not only "encouraged" to take on all the positions of the religion, but the positions themselves are often the logical conclusions to the illogical premise.
An analogy: If we start with the idea that Human life has no inherent value, it's not a massive leap to reach genocide. The counterbalance is the idea that Humans are made in the image of God, and every soul is inherently precious due to that fact alone. If you reject that for, say, a practical argument about how Humans might do good things, you run into the fact that Humans also do bad things. Like, clearly, demonstrably bad things, without a second thought. There would, by that logic, be some Humans who literally don't deserve to live. You can only kick the can down the road until Timmy here turns into a serial killer or something.
Is that the right answer? If we have a solid moral stance based on principles, then it's not. Not even close. The idea itself is so far outside of the window of reasonable discourse that even bringing it up is taboo.
But if you don't, then... why not?