Christianity and freedom
I think you have been a bit selective in your reading of history, Roger. You are quite right in drawing our attention to the many atrocities committed in the name of Christ, but you have not chosen to notice where we in the west have ended up. We do have democracies in place. We do have freedom of religion - though that is fast being eroded away. We do have freedom of speech. So many Christians put their lives on the line to achieve these freedoms because they understood that people - every person - is intrinsically valuable because he/ she is made in God's image.
The Westminster system of democracy arose in a context of Christians trying to work out the best way of governing. There were the battles between the kings and the people that led eventually to the Magna Carta. There were the battles to separate church from state. NOT religion from state. That is impossible. But separating the institution of the church from the state is a thoroughly biblical principle. Jesus himself validated the state as separate from the church by saying '...give to Caesar what belongs to Caesar and to God what belongs to God'. Incidentally, Islam has no such separation. For them the 'church' - that is, Islam, is the state.
So while there are all sorts of dark periods in church history, there is also a movement towards the free and open society we have now. Free and open societies like ours are a rarity in human history.