It's the devil getting you to fall for the old lie that he doesn't exist.

Sure, I'll be that guy.

Moral relativism is absolutely real. This is because, to quote one of my favorite authors, if you grind down reality to the finest powder and filter it through the finest sieve, you will find not one molecule of justice and not one atom of mercy. These things aren't real, in the tangible sense. We made them up, and we're the only beings in this solar system that engage with them. Nature is red in tooth and claw, and horrific ways to die are the norm, not the exception.

We simply do not, and cannot, have a real, tangible, objective measure of "moral" or "immoral". Every single attempt to identify one always boils down to either emotional appeals with a dash of "I'll know it when I see it" in the secular spheres or "my holy book says so" proscriptions in the religious spheres.

That being said, just because something isn't tangible and real doesn't mean we don't engage with it. Math isn't real either; it's a way to identify patterns in nature using an entirely artificial method of symbology, and make predictions using that symbology.

Ergo, moral concerns and judgements still will, and more or less must, happen, given mankind's unique ability of all animals to engage with metaphysical concepts and thinking. Note I use "metaphysical" to mean "beyond physical", such as math or future planning, and not to mean "supernatural" or "theological" or such.

With terms defined, let's hop back to moral relativism. Moral relativism is the understanding that, given there is no objective morality, we can't expect every person to make the same moral judgements for a given scenario. We must instead understand that other people make their judgements through their own understanding of morality, the same as we (in the sense of you or I) do, and while geographically and culturally similar groups often have similar moral mores, those separated by time, distance, or significant cultural institutions will generally not.

We must, keeping these things in mind, now understand that, from the perspective of the average sandperson goatfucker, they are not only not doing anything wrong, they are quite often doing what is good and moral. Their culture and morals allow, and in some ways require, them to act the way they do. They are not knowingly acting in a way we would define as evil; they act with the full support of both their conscience and their institutions.

That is, in it's entirety, the concept of moral relativism.

Please note that this DOES NOT MEAN you cannot make moral judgements. You absolutely can, and should; the others certainly will. You must simply understand that others are not acting AGAINST YOUR morality, but rather IN FAVOR of THEIR morality.

You can recognize that morality is relative and still absolutely desire to wipe certain moralities (as well as their underlying institutions and cultures) off the face of the globe because what they consider good, right, and proper, you consider bad, evil, and immoral.

Its honestly a pretty easy thing to define even, because its usually just the difference between malice and ignorance. Its only relevant whatsoever when the excuse of "these people are retarded" is enough to defuse the anger at most of what they are doing. Something like circumcision making an iota of sense in a sweaty, desert culture centuries before hygiene became kinda better to prevent much worse conditions, but being nothing but evil without those factors combined.

Problem is that 99% of the people using it are the type of Lefties that would never dare to say the very losers they are describing are ignorant idiots, so it becomes a long convoluted chain of excuses and jumping through hoops to avoid sounding bigoted.