Axel-
He did so by vandalizing their user pages. I told him to stop. In response he vandalized mine.
And so you got angry and banned him.
Wrong. I warned him, he continued his vandalism spree, I banned him. I would have banned him if he had vandalized any other user page. I and other developers have long had the authority to ban signed in users in cases of vandalism. I did not even use developer privileges -- any other sysop could have, and should have done the same. You should be more worried about users who call all other Wikipedians nazis and refer to the whole project as "Nazipedia" than accusing those who try to maintain some semblance of sanity of abusing power. Nonsensical accusations like that are poisoning the atmosphere of this project, and I would very much appreciate it if you would keep them to yourself.
Regards,
Erik