His second and bigger mistake was continuing astride for years even after several people expressed concern, told him he doesn't know the language, and explained that his editing was doing real damage to perception of the language.
It's not right to treat him like a vandal, but the second mistake is good cause for being a little bit more forceful and public with the rebuke.
TBH it was a failure of the community to even allow the situation to get this bad.
Whether this is willfully malicious, or stupid to the point of maliciousness seems like splitting hairs.
Honestly, I feel differently about those two situations, especially since it affects the outcome. It looks like the Scots speakers who engaged with him have managed to work him into a fix. Good for them.
Treating this guy like some sort of vandal isn't right. To be honest, it doesn't look like there are very many Scots contributors, so perhaps it should just be dumped as a project since it doesn't look like there are many Scots readers either.
EDIT: Ah fortunately, they've been in touch with him³ and he feels awful that he upset people². I am glad there are kind people in the world that know how to help people be contributors.
¹ https://en.wikipedia.org/wiki/Ecce_Homo_(Mart%C3%ADnez_and_G...
² https://www.reddit.com/r/linguistics/comments/igbbh2/the_sco...
³ https://twitter.com/Cobradile94/status/1298321034530246658?s...