I have a suspicion that the perpetrator might be psychotic, which, if true, raises questions on how he was working as a psychiatrist. In any case, we'll find out at some point, because he will surely be assessed.
The next thing would be for someone to drive through a women's march due to fear of patriarchy. Or mass-shoot people praying in a mosque because of fear of over-christianization.
I can't find any source saying he hated Christianity. You seem to, again, be making up facts so they fit your interpretation of things. All sources I have say his most likely motive was fear of "over-islamization".
"Kranke Welt", as one eye-witness said. Something needs to change in this country, I hope we can all agree on that. And if you don't think so, I won't bother arguing with you. I'm just too tired of all of this.