I thought exactly that. Opened the post, upvoted this thread.

However couldn't not Google it, and it may be on purpose.

evilness

noun

evil·​ness

: the quality of being evil : badness

https://www.merriam-webster.com/dictionary/evilness

While it does sound better with just "evil", I wonder if they wished to exactly convey that what is being created is the quality of being evil in some people. All in all, that goes under the umbrella of evil, sure. But if we replace "evilness" with "badness", it no longer sounds worse than the alternative, just "inequality creates bad". Ofc you can't compare directly like that, I'm just trying to make the point that black civil activist haven't historically been that bad at language use, so perhaps we're just feeling the more colloquial version but that this may be prescriptively better, idk.

I'm no languinolologist.