What does evil even mean? Evil as defined by whom, because of what exactly? Good and evil are in reality subjective terms, and they have meant a whole lot of different things throughout history. It used to be that simply not worshipping the right god in the right way was a sign of blasphemy and thus evil. It still is like that in some parts of the world. Apostasy is punishable by death here and there.
If we're going to get this "real" in a gaming board discussion then we should probably not complete skate over what "evil" actually means. But this is usually done for expediency in any gaming context, because good just is, and so is evil. And that's okay, because playing a game usually means trying to work our way through a story rather than getting into the nitty-gritty of philosophy.
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Well I would encourage you not to conflate how our world works with how D&D works. In our world there are no Demons, Gods or Devils, or at least no empirical proof of them. We would classify evil as a mental health issue or unhealthy pathology.
However, if you read the PHB it does lay this stuff out. As has been mentioned, evil in D&D is a metaphysical force.
-The Hells are made of Evil.
-The creatures that inhabit them are made of that substance and so are actual evil.
-Evil seeks to perpetuate itself in D&D.
-Alignment dictates how that evil is expressed.
-Fiends gain power through corruption, subjugation and suffering they inflict on others.
As for "having tea with Orcs" as funny as that is this isn't a discussion about what actions we should or shouldn't take in the actual game. Orcs, whatever the underlying narrative and history are still a threat. But really anyone in the world can be a threat - depending. There are dangerous and selfish Gnomes and halflings. As a player you can deal with them however you see fit.
I am aware that D&D has some rather more tangible expressions of both good and evil. But my point is, "good" and "evil" is not that deeply defined. Part of the game, essentially a premise for the game world making sense, is that we generally speaking accept its notions of what good and evil is, without trying to analyze them into oblivion and bog the game down with all the shades of gray that are part of the real world.
That being said, the "tea with orcs" thing is of course largely a joke, but not entirely, because technically orcs are people too, and technically there might be a solution to the problem of villages getting slaughtered by orcs that does not involve waging a genocidal crusade against the orcs. Technically there might be some pathway to a mutually acceptable solution where everybody gets to live in peace. The greenies raise squigs and sell delicious pork and the humies farm veggies, and then there's peace and happy times, and occasionally they join forces and raid the dwarf ale stores. Good times. And maybe a franchise mixup, whatever. But if this is possible then is it not the duty of any good and civilized adventurer to seek out this path first and foremost? Is it then not actually quite evil to just be prejudiced against the orcs and condemn them to genocide, simply for being orcs?
Amusingly, even Baldur's Gate 2 had some fun with these angles. Remember how Keldorn was being a bit of a jerk for ragging on Viconia, just because she was a drow? Well, he was. But at the same time he was undeniably a lawful good character and she was undeniably an evil Shar-worshipper. The whole thing further got nuanced by Keldorn's family quest showing him to have more than a few broomsticks up his rear, whereas Vicky turned out to be strongly shaped by her tragic backstory rather than just evil for the sake of it.
And that is how I feel we ought to use our somewhat more complex real world understanding of what good and evil is. Not to get offended over this or that detail in the game, but to look for funny angles and odd twists and maybe occasionally reflect over the contrast between the game world's relative simplicity and the real world's almost impenetrable shades of gray.
Case in point, there is a reasonable enough complaint about how the treatment of drow in D&D has unpleasant connotations for a lot of real world people. While the game world is a fair bit deeper than "black elf is evil elf", the reality is that the sentiment is largely validated in a lot of stories, where all the white elves range from amazing to meh whereas all the black elves are fanatic followers of the hindparts for headwear fashion trend. It's not real nice, is it? So making this part more nuanced is quite reasonable, because it does express a game world situation in a way that is obviously painful to a lot of people.
But the reasoning should not be extended to the point where all races that are humanoid and intelligent must be considered "people" and treated as such, because otherwise we are essentially justifying racism against some minority group. That takes a reasonable perspective and dials it way up to eleventy. It is not racist to consider orcs evil, because they are not humans and they are not demonstrably capable of acting humanely. For game world purposes, it really does not have to go deeper than that.
