“psycholinguistic effect”: that’s so ethereal as to be meaningless and unfalsifiable. That’s the insidious part too with a lot of anti-racism. You can scarcely disprove or prove any of it.
I've seen posts elsewhere that claim the etymology of blacklist, specifically, isn't based on this metaphor, but this metaphor exists throughout English. Consider this line from A Midsummer Night's Dream, "Not Hermia but Helena I love. Who will not change a raven for a dove?" where light > dark is so obvious that all you have to do is compare one girl to a dark bird and one to a light bird to make your point.
Again, it's possible to go to far with this (e.g. whitespace), but that's a question of where to draw the line, not if.
If we're going to make a change to language then it should be to stop describing people as black or white. Which was never particularly accurate to begin with, since "black people" are really varying shades of brown and "white people" are varying shades of pink to light brown anyway.
I assume it's too much to ask that we stop categorizing people by "race" entirely.
There is an entire TVTropes page dedicated to "Dark Is Not Evil" and it's not a purely subversive trope either, quite popular in media as well.
There is also plenty of media (and culture) where darkness is sacred and pure, not evil or cold. Consider the dwarves in the discworld series that hold this belief. For more real-life examples, the hebrew bible generally refers to shadows and darkness as good since when you live in a desert, those things will bring you some fresh air and protection from the sun.
Superman: Literally powered by the light of the sun, boy scout who never breaks the rules, hard-working member of the proletariat.
Batman: Tortured soul with tragic backstory, lawless vigilante, billionaire (regarded as evil in popular media, cf. Lex Luthor).
The darkness in Batman is the adversity the hero has to overcome. It's integral to the story but it isn't pleasant. You can't imagine the young Bruce Wayne wishing for somebody to murder his parents so he can grow up to don a bat suit and punch criminals in dark of night.
And so it is with the other common depictions of darkness in hero types -- an internal struggle, not a desired characteristic in itself.
You can find the odd situation where darkness actually is positively desirable in itself, but not enough to overshadow all of the more common ones where it isn't.
I don't agree with your assessment of Batman and I would point out that Batman isn't regarded as evil in popular media (and even if he was, Superman was evil plenty of times, see Superman Red Son)
Lastly, I would mention that in hero types, a internal struggle is usually desired to counterbalance or embolden external conflict. Even superman has internal conflicts.
For example, I have black eyes and hair, but I never once felt I was less a person because of this abstract generalization. I don't recall ever having made such a connection until when I started thinking about arguing against the reasoning behind banning blacklist.
Similarly, obsidian and black granite are typically considered beautiful. When I choose the color of my phone or display or car, I don't think white = good or black = bad. When there is context, this abstract association does not come to mind; rather, for example, I think that white can distract from the screen of a phone, or that it wears its stains easily. Or when I choose a dark theme for my editor and apps for ease of viewing in low light. Or with clothes; I don't think (black = bad) when I wear my black clothing.
So this is why I disagree with this; we associate ourselves with black things and make color judgments all the time, but rarely does the value judgment of white = good, black = bad figure in these judgments (modulo actual reasons in particular contexts, e.g. stains easily, vs. hard to see in low light). An argument that this "psycholinguistic effect" actually happens also needs to address the many other categories in which we make color judgments in our lives. (Question: does a strongly racist person significantly and subconsciously disassociate themselves with black products more than the average person? Beyond conscious decision on color to symbolize their attitude, and the subconscious generalization from this symbolic desire.)
With respect to blacklist, it seems to me that this is the most unfortunate product about the whole discussion. I believe that hardly anyone has associated the word "blacklist" with derogatory attitudes against blacks, but now someone has made "blacklist" and black of race so tightly bound semantically that we can't help but think of race when we now see the word blacklist --- even when nothing close is ever being intended by the people who use the word.
I think that my model that there are many semantic categories of blackness for which the value judgment (white = good, black = bad) doesn't figure at all as a "psycholinguistic effect" is more accurate. If this is indeed the case, then ironically the whole discussion over "blacklist" has caused more harm than good, since it is enlarging the collection of meanings that remind people of derogatory attitudes against blacks.