They were bad.
Reel ’em in with a bold, controversial statement. I sure know how to keep a captive audience.
Let’s trying something a little more specific:
The Nazi movement had a strong religious component, and strong ties to the Catholic Church. Most Nazis were Christians.
However: The Nazis were bad for reasons almost entirely unrelated to Christianity.
Similarly: Many Christians are good. Those who are bad are, almost universally, bad for reasons entirely unrelated to Nazism.
My point is this:
When atheists bring up the fact that Nazi Germany banned books which promoted Darwinism or disparaged Christianity, it’s not because we’re claiming that all Christianity is evil and all Christians are evil because of some Nazi connection.