When "it's what my character would do" is actually true.

[Satinavian]

This may or may not be viable as an argument about the way the game rules are set up, but that's more because D&D doesn't do anything but arbitrarily staple "evil" to the act. There are other things that actually meet a real-world definition of evil that are better examples. (For the record, I want the rampant use of undead to be inherently evil in my D&D, but the efforts to figure out how to make it actually fit the definition, rather than having a specific exception that includes it as part of the definition by arbitrary labeling, is several threads' worth of conversation of its own.)

Yes, some elements of what counts as good or evil seem pretty arbitrary with undead and poison being the most obvious. But i don't think that need fxing by attaching unpreasant consequences to necromancy. If you really play with cosmic alignments, it is enough to say those are evil just because. Because cosmic alignment is kinda arbitrary. If it bothers people so much that they need it fixed, i would rather declare it not evil instead of making it harmful.

Why does he need to think "tolerance and equality are nice?" He thinks both are stupid ideas promoted by swindlers who want to take what they can't otherwise have. And while he may or may not have any problem with swindling, he does think that it's stupid to fall for it, and he's too smart, clever, and strong to fall for it. Sure, he's evil. Evil means smart. Good means dumb, gullible, and pathetic. It's disgusting to be Good. So why would he want to taint himself with that label, let alone do anything to earn it?

No, he doesnt subscribe to the philosophy of evil. Only to Kender based racism. He genuinely values tolerance and equality between all non-Kender and wants to be a good, reliable, helpful member of the non-Kender community. He probably thinks of himself as tolerant and helpful and even good (if not confronted with alignment detection) because Kender don't really count in his mind. He is still totally evil but you wouldn't know it if you never see him interacting with Kender or talking about them.

"I'm smart for wanting a good life." Why does he need to object to the label of his actions being 'evil?' He doesn't see anything wrong with being evil.

He doesn't see anything wrong with swindling people. He might still see lots of things wrong with all other kinds of evil. The grouping of things into evil and non evil is just not particular useful to describe his autlook.

That's only one possible way to look at it, but remember: evil in D&D is a morality. It isn't merely "actively not caring about being good." It is something that has its own positions and moral codes. You can be good or evil to a degree without deliberately signing on to such codes, but those codes exist and people can have moral convictions about them. Without being cartoonish.

Yes, that is the core of it. Being evil is about doing evil things. It is not about subscribing to the moral philosophy of evil at all. Sure, some people do follow some philosophy of evil. But most people, even evil people don't. And most philosophes don't fit particularly neatly into the 9 alignment boxes anyway, so yeah.

Why wouldn't they? There's nothing wrong with being evil! In fact, being evil is RIGHT, and being good is wrong.

Because most evil people are not happy about the evil others do and quite comfortable with the good others do. Because evil tends to come at a cost to others or society and good comes with altruism and benefitting others or society. There is no question whatsoever what the typical evil person wants to experience and that is not different from what a good person wants to experience. It is only when it comes to reciprocity, when the difference show themself. That is why you will find very few people believing evil is right, if that includes evil that they have no intent to do themself and might be exposed to.

You're looking at it from a culturally Good perspective.

I actually aimed for neutral, but yes, society influences morals and creeds far more than personal alignment. I also rarely use evil cultures as over the top as the Drow because those tend to be utterly unsustainable if one thinks a couple of minutes about them. The evil cultures i do use have usually only one or a few established evil practices or traditions. There might be a tyranny cracking down hard on dissent at the expense of justice, there might be extreme stratification and certain classes treated quite ****ty, there might be widespread corruption, there might be established slavery, there might be a culture accepting of raiding glorifying successful raiders and of course there might be one making heavy use of undead. But i tend to not mix those and am generally carefully with the backstabbbing and other destructive tendencies. If people at the table ask themself "How has this not imploded years ago ?", i have done something wrong.
So even evil cultures don't really have a philosophy of evil. If chosing what fits them more and shown the box with all evil ideals and one with good ideals, they would probably complain a lot about nothing fitting but eventually choosing the good one because the evil one just contains way to much destructive stuff they can't tolerate.

And both are evil. Unashamedly so. Both view what they do as perfectly right and acceptable. They know it's evil. They also think that it being evil is a plus. Because they're evil, which means they're smart and powerful and unafraid to use their power. Only weaklings feel the need to curtail their power for simpering emotions like :spits: empathy.

Of course both are very evil. That is why i chose them as examples of evil gods. But both do not champion the cause of cosmic evil at all and both don't care about the conflict of cosmic good and cosmic evil.
And that makes them good examples to the strand of argumentation i responded to here where evil gods were presented as champions of Evil.

Which is perfectly doable when everyone agrees that, say, indiscriminate killing is evil, but not everybody agrees that that makes it wrong.

But the vast majority of evil people agree that indiscriminate killing is quite wrong.