You have to define what Christian is, and since there is obviously numerous definitions, you must make a differentiation. By your logic, every single European around the time of WW2 were Christians. Which would make the term itself rather irrelevant because it would be merely a cultural label as opposed to an actual religious one.
In my view people like Hitler neither identified themselves as Christians in the religious sense, namely acknowledging that they believe Jesus is son of God, source of salvation, and believe in living under Biblical tenets, nor did they act like it even if they verbally stated so.
There's calling yourself a Christian, being called a Christian, and acting like one. Far as I'm concerned, such people are only called Christian without any definition of the term, nor an explanation why, and then people just take it from there without further thinking. I mean how do you KNOW that Hitler was a "Christian" and that all Nazis were? There were Jews in the Nazi regime, in fact, and even members of the Nazi leadership knew about it but did nothing.
There were at times that Hitler described himself, vaguely, as having some association with Christianity, but other times he despised it.
Again, your point is meaningless without a definition of what Christian means, and that Good means. To make it stronger, include characteristics that prove contrary (after all, a characteristic of good cannot exist without a characteristic of bad).