As long as humanity has been kicking around, there have been greedy, self-serving people who will use whatever means possible (including religion) to reach their goals, whatever they may be. This doesn't make them religious people. Just people with a means to an end. It goes both ways.
Hitler used the German church to rise to power because he knew it would resonate with certain populations. Was he a Christian? I would argue no.
The Catholic Church does not speak on behalf of all Christians. They don't now and they didn't in the past. Dietrich Bonhoeffer was one of the greatest Christian theologen's of our time and he not only opposed the Nazi's, he played a large part in informing the British government what was going on in Germany and was part of a plot to assassinate HItler.
While he didn't begin or finish the quest of the abolition of slavery, William Wilberforce was a devout Christian who worked tirelessly to end the slave trade.
I agree that good men will do good things and bad men will do bad things.
Almost everyday there is a thread somewhere on NS trying to debunk God and religion, but the moment something bad happens, the entire NS population is offering prayers to the victims families. I'm not commenting one way or another and I'm not trying to take away from people offering their condolences, but it is a relevant observation.
Sorry for my scattered thoughts.