"Evil" is a term that really only belongs to theology. The thing about evil is that evil (and the kind of good that goes with evil) is that they're absolute. Things are good or evil "by nature" - from no particular perspective. That's nonsense. We recognize that some things are good or bad (bad, not "evil") from our perspective, but that the bourgeoisie have an opposed view. What they do is literally good from their perspective. We can't, therefore, convince the bourgeoisie to give up power with moralistic arguments (because from their perspective they are right), it's impossible. We have to actually overthrow them. Recognizing the necessity of the violent overthrow of the current order the, IMO, the fundamental belief of Marxism.
Basically, good and bad = good and bad for something, some person, some group, etc. Good and evil = supposedly good and bad per se. But that's nonsense, and only a cloak that the ruling class uses to present what is good for them as good per se.
Although I disagree with ilyenkov on the specific use of "evil" because I think we should just use the term for egregious shit without fear of being mistaken for religious positions, I think this relativity it absolutely not "it's all relative dude" but an understanding that the only absolute is between relativity. As analogy, location in space is relative; there is no way to say where something is without relation to another. That relation itself is absolute and can be the basis of a metaphysics much more complex than the dudebro shit. This is what made Hegel revolutionary in his thinking and Marx after. Keeping that analogy going, you can do the same thing with speeds: only meaningful relative to another but that relativity gives MORE clarity about speed than trying to analyze it alone. In fact, talking about speed without a reference frame can only cause you to miss the beauty of physics! It also makes acceleration uniquely interesting in it's absoluteness, because it's speed relative to speed WITHIN THE SAME OBJECT.
Marx loved this shit, the lovable nerdy shithead, and wanted to apply as rigorous of thinking to society possible with the help of the natural sciences which had such realizations. "Relative" in it's vulgar form is dumb and only leads to inconclusive positions.
Maybe that was what you meant by your joke but don't want a passerby to think we're vulgar about this
Expanding on this slightly, a question arises of "why not simply pick a perspective and go with it?" Meaning, in our developed societies, simply viewing evil as bad from the perspective of the proletariat. And some theorists, including Lenin, have taken an approach similar to this. But a Marxist understanding of the world can never pick one perspective with the full exclusion of others. This new concept of evil remains subordinated to class and inferior to it in explanative power.
The liberal concept of evil does fully exclude other perspectives, and can be used to explain the actions of "enemy" nations, turning them into the Axis of Evil again and again. Their leaders are personally evil, meaning, depending on the flavor of the liberal, being somewhere on the spectrum between mentally ill and in league with Satan. This kind of narrative is great if you want to do coups.
If we call, for example, Ronald Reagan evil, we do not mean it as personally evil, but evil as a function of his position in society. We can not explain his actions as being caused by some metaphysical evil, because our evil is directly and consciously linked to class. To fight this kind of evil is not to fight a personification of it, but the system itself.
This new concept of evil remains subordinated to class and inferior to it in explanative power.
materialism lets us look critically at aspects of bourgeois morality that exist at odds with the interests of humanity, but class on its own isn't a complete blueprint for proletarian ethics. not all social interactions reduce to class relations, and you also have to account for nonhuman sentients who are outside of society altogether
Yes, this new concept of evil exists within the chosen perspective, and we can not hope to understand reality with just one perspective. That does not stop us from examining this single relation.