In the world of D&D Demons, and devils and Yugoloths are part of the natural order. They are a side effect of mortal evil as an essence that can be distilled into actual objects and creatures that are imbued with that essence. It's genesis is in mortal need and conflict.
The Githyanki are Lawful Evil. They kill and plunder on the Astral Plane. They do it for 3 main reasons.
1) Resources they feel they are owed because of the war they fight against the Illithid.
2) Anyone who can't defend themselves from the Githyanki will eventually become thralls for the Illithid and they will have to kill them anyway.
3) To train and prepare their own people to fight the Illithids. Inexperienced Githyanki have a chance to increase their skills in raiding.
They are a militant people who have done more to destroy the Illithids than anyone (to the point of near extinction which is likely what brings us to the events of this story) - and have never forgotten that no one helped them when they were slaves.
The Githyanki create evil because of their actions. This evil becomes part of The Hells in a number of ways I won't delve into. It is 100% part of the natural order.
Evil is as valid a point of view as good. Oftentimes Evil can be just as or much more effective than good in making the realms a better place.
Speaking of Good, there are types of good that are completely ineffective (self righteousness) or even useless like innocence. Just like there is Evil that can be self-destructive or too narcissistic to be useful.
The Hag is part of nature. She is part of the Dark Feywild. Yes, she is a predator, and predators seek prey, always. They seek the weakest in the specifies to prey on always, like all predators do. That prey just happens to be us so we label it evil.
Yet if you are strong, wise, and diplomatic you can coexist with the Hag just fine. The Gur do it because they pass around the wisdom of such things. The Gur are not evil.
