Thanks.
On the black = evil association, I find it very interesting that many are doing it, while fewer notice that the "White" elves aren't much better.
In the version I read (not really delving into their background, so it's most probably from 3e), Drows are cursed not to withstand daylight, so they had to take refuge to the Underdark, where there is a corrupting influence that made them (and other Underdark denizens) more susceptible to evil. So basically, they are shunned for being Evil while forced to live in an Evil-corrupting place, much like poor people in the 18th century were blamed for thievery when they had no other means of sustenance. It's not as bad as if they had really free will (not having to live in the Underdark) and had chosen to be Evil without external influence. The existence of the Lorendrow, who lived in the shade of a jungle and weren't exposed to the Underdark and turned out to be Good is evidence that the regular drows can't be blamed for their evil ways, their free will reduced by the magical nature of their environment. I agree that it's conceptually difficult to imagine that "the rocks around me made me kill puppies" but it's what perspire from their lore, and with magic, why not?
On the contrary, regular Elves are rooted for, despite none of their lore being better. I mean, their chief god is a major dick, and their inspiration isn't better. The sidhe from English lore doesn't look to be good, Tolkien Elves are major dicks : the ME elves either refused to follow the Good gods of the setting to the undying lands, or went back pushed by pride (and being cursed by their gods for this). They are mostly aloof and unrelatable, and I really can't see Thranduil as good, for example. The most relatable ones are... half-elves like Elrond (morally saved by their human half?). Even in D&D lore, they have a genocidal history. The 3.5 MM entry for quaggoth states that:
Quaggoths were never an enlightened species, but they were not always the brutal Underdark denizens they are today. In a distant age, quaggoth tribes dwelled upon the surface as nocturnal arboreal hunters, possessing their own language and culture. When elves appeared in the mortal realm, they clashed with the Quaggoths, eventually driving them to near extinction. Only by fleeing deep into The Underdark did the Quaggoths survive.
As they passed the ages deep beneath the world, the quaggoths’ fur lost its color and their vision adapted to the Darkness, even as the constant danger and Weird Magic of their new realm transformed them. Turning increasingly brutal and savage, they ate whatever food they could find—and when they could not find it, they preyed on each other. As cannibalism became part of their culture, their past was abandoned.
So basically, White Elves get away with quasi-genocide, cultural genocide at least, forcing the native quaggoth to take refuge to a morality-warping place. And they are the "good" species. They can be of any alignment, so there is no external, metaphysical Evil that made them choose genocide over cohabitation with the native Quaggoth who dwelled in the trees before them, or that forces them to revere Corellon as Good despite what he did to Drows. Is it only because they are White with blond hair that they can escape scrutiny in 2020? Or because we accept that history is written by the winners (and therefore we have countless novels about Drows being evil while the Quaggoth Genocide is mostly kept under the carpet? Behaving awfuul seems to be a thing from the Elf species, irrespective of their skin colour, with underdark denizen pushing it to 11 because of external causes.