The race can be any alignment except for goodnote , also doubles as an example of Inverted Always Lawful Good.
The race is led by an emperor who does not take well to traitors and orders the instant death of those who do not conform to his evil beliefs - most, therefore, choose to go with evil's path for the sake of their lives.
Alternately, the race is from a Death World where only the violently selfish survive.
Alternately, they were artificially created to be evil/so ravenously violent that they're functionally evil.
Alternately, the race follows a full-blown Religion of Evil—complete with a "Might Makes Right" morality (which admittedly raises questions on if they consider themselves evil)—and the best a heretic might hope for is to be executed for said heresy instead of ending up a Butt Monkey.
Alternately, you have to be evil to be a member of the race.
Alternately, their gods simply made them that way.
Characters find an evil dragon, except that it is being held prisoner by The Hero, and expresses nothing but concern for them.
The race isn't actually evil, but it's portrayed as such due to a massive propaganda campaign. The heroes are actually working for a Grey Morality side.
The race isn't actually evil; they're just pretending to be evil so that the real bad guys or an actualAlways Chaotic Evil race doesn't kill them.
The race isn't actually evil, but their culture demands strict laws and brutal punishments, so it looks violently repressive from the outside.
The 'evil demon race' turns out to not be entirely evil, since some are on the good side, until the inbred evil desires in their blood cause the good demons to switch sides when things start to get tough. Visa versa for the 'evil' characters allied with the hero's side.
Zig Zagged: A race is forced to be evil because of an Evil Overlord. When he is defeated, they try to be good, but social stigma force them to work only for other evil overlords. A minority of them works to raise the public opinion and manage, in the end, to redeem the race, giving them the opportunity to live honest lives. Only, it's a conspiracy to infiltrate the human society. Again, they manage to clean their public image, only to find integration too hard, so they try to conquer the world. Defeated, they choose to lose all power and strength, so humans won't fear them anymore and they can start playing good. So they became extreme capitalists, and brought the civilization to an evil dystopia.
Averted: There is no 'evil demon race'. Evil is made up of races that are also just as likely to be good.
The race come from hell itself - if we portrayed them as being friendly in any way on a popular show, the Moral Guardians might not be too happy with us.
Lampshaded: The heroes ask a member of the 'evil demon race' why he's serving the villain, and he answers with "Haven't you seen? The whole race is evil!"
Invoked: A race of demonic creatures raise their children to act evil because enough of them are mean that they'll probably end up stereotyped as evil anyway, and they don't want the trouble of being a nice person struggling against the views of others.
Exploited: Bob, a Sociopathic Hero, wants to kill people, but he can't or else he'll be seen as evil, so he finds the always chaotic evil race and can kill as many as he likes while still being seen as morally good.
A bright member of the race begins preaching that they all have free will and do not have to simply be evil. This gains credibility among everyone, some members turn good, some remain evil. The ones who remain evil feel reinvigorated because they have now chosen evil, and become more evil than ever. The evil member proceed to kill Messianic Archetype, for the Evilulz.
Discussed: "See, if this were a fantasy book, I wouldn't be able to be nice to you guys, since demons have to be evil and all. You guys are lucky!"
Conversed: "And of course, in those RPGs I play, you never get to meet, say, an affectionate, cheery demon, or a pleasant and polite swamp monster. What a shame, don't you think?"
The demon race is all evil...because the villain is controlling their minds and thoughts. Eventually, they are freed from this, but their all-evil image gains them the hate of others and the race faces serious troubles as they struggle to cope in the world.
The presence of an Always Chaotic Evil race leads to discussions of moral relativism vs. moral absolutism and whether or not we can force our moral standards on a race.
Alternately, everyone assumes that an alien race is all evil...thus subjecting those members of it who are good to prejudice.
The Demons spend as much time fighting themselves and imposing Draconic laws upon their subjects as they do fighting the heroes.
Having been freed and hated on, they give up and go with being evil anyway.
The discussion ends by pointing out that, while all over races engage in evil occasionally, all the the ACE race does is evil.
The setting is a crapsack world (to an extent). The evil race is powerful and a threat to all the other races. Everyone has tried to make peace/form an agreement with the evil race but it always fails. Some even looked into the very heart of the evil race to find anything redeemable about them, only to find nothing but pure raw malevolence. It's made clear to everyone that the evil race is irredeemable, but what to do about them is the big question. The discussions of moral relativism vs. moral absolutism applies to the scale of idealism vs cynicism in both the setting and with the characters themselves. For example, on the idealistic side, the heroes find the power to seal the evil race off from the rest of the world so they can no longer cause any harm; that way, the heroes would be able to triumph without having to make morally questionable decisions. On the cynical side, if such methods like sealing the evil race away prove to be ineffective and destroying them all is the only way to truly stop them, the heroes may end having to rethink their values, understanding that their ideals are too unrealistic to work in the setting, thus adopting the moral relativism thinking; they are prepared to shoulder the weight of morally questionable actions for the sake of protecting the world from an irredeemable evil, because letting such an evil live might lead to more devastating consequences for the rest of the world.
The alien race is assumed to be evil because refugees from scores of other planets have arrived to warn others.
The Demons maintain their dominion through twisted rationality, emphasizing that they're evil, not stupid.