Yes, it's Marxists who define Marxism as "dialectical materialism," not their enemies.
Gnosticism is a syncretic religion, which means it steals superstitions from any source, and the dialectic was taken from the ancient Greek religion of Hermeticism, which claimed that "opposite things are the same."
If you Google "Marxism is Gnosticism," you will find a lot of information.
The dialectic was formalized by Hegel, after Kant wrote his "Critique of Pure Reason," which was a religious reaction against the advance of logic. Kant claimed that "there are other ways to know other than reason." Kant claimed that whatever you feel like is as valid as logic and reason.
So Kant gave a bullshit excuse to religions to claim that faith is equally as valid as Aristotelian logic. It's just a lie, but that left religions without a way to argue, so Hegel made up the dialectic as an irrational way to argue.
The dialectic calls anything the "thesis," its perfect opposite the "antithesis," and claims that the thesis and antithesis are the same thing, and it is called the "synthesis."
Hence, the dialectic is absolutely incompatible with Aristotelian logic, which is based on the principle of non-contradiction: "A statement is either true or false."
The dialectic claims that true and false are "the same thing." It's a superstition, rigorously, mathematically demonstrable as false because it contradicts itself as the starting point.
Proof by contradiction is the most rigorous mathematical proof of falsehood, so Marxism is RIGOROUSLY false.
The dialectic is idealism, which is the complete opposite of materialism. Materialism believes in objective truths, independent of opinion, and idealism believes that humans are gods with magical powers, which can create reality itself with the power of the mind.
So Engels bullshitted that if the dialectic is the opposite of materialism, they are the same thing: "dialectical materialism." And since Engels paid Marx's wages, Engels made Marx adopt the "Draft of a Communist Confession of Faith" as what you know today as Marx's "Communist Manifesto," which is a manifesto of FAITH. It's a religion.
Dialectical materialism is what George Orwell denounced as totalitarian "doublethink" and "doublespeak."
Example:
Justice is the opposite of injustice, so "social justice" is both justice and injustice simultaneously.
Communism is the opposite of capitalism, so it's the same thing: fascism or "the third way." That's why Nazi means National SOCIALIST.
Communists call themselves "liberals", when liberalism is the antithesis of socialism.
Men are the same as women, hence men are "trans women."
Property is "theft."
Paid, voluntary work is "exploitation."
Communist dictatorship is "democracy."
Che Guevara is the flag of gays (he actually executed gays in a concentration camp, and was the ultimate homophobe).
And so on. Every word used by a Marxist means the opposite, so the entire Marxist discourse is a method for lying and gaslighting.
That's why Marxists call anybody who believes them a "useful idi*t." There is a Wikipedia page for the phrase.