His first mistake, which should be treated with graciousness and care, was a case of reach exceeding grasp.

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.