The Nazi was banned for being "unacceptable and people wanting nothing to do with him".
KDE is contributors in a broad sense, always had been. From coders to bug reporters. People who never interacted before with the project in any capacity can fairly be described as "not KDE".
If there is a code of conduct, and it's enforced selectively, is it a code of conduct? If I stab a Nazi, I may have done the morally right, I'm still going to jail.
On the lessons, that's not what I read.