Blaming all Christianity is no different than blaming all of Islam or all Americans or all Russians, all Chinese, etc. for the ills perpetrated by a tiny minority with the power and will to do evil things.
Terrible people, just like extremists exploiting any ideal, veneer themselves in our cultural unifying ideals. That doesn't mean they represent those ideals. Tangerine Caligula, Florida Man, Texas Turd claim to represent democracy – but we discern that they are authoritarian fascists. If religion wasn't part of the equation, horrible people would still be horrible and would still find their way to power veneered in some otherwise higher ideal.
Also, some would argue that God does do something about it. God makes us able to recognize the perfidy and to act against it. If we aren't choosing to do that, God is not to blame. Blaming God for for every human perpetrated evil – and lack of action by human systems and humans – is just the flipside of the immaturity of spiritual discernment in fundamentalist evangelicalism's magical sky daddy wish slave.
At what point do we stop railing against God and blame the people doing the evil to people? We need to hold those individuals accountable instead of blaming an ideal or entity we cannot hold accountable. Instead of blaming Christianity, try what the Bible itself tells us: "You will know them by their fruits" – i.e., by the things they do and say. True Christians are followers of Christ Jesus; Jesus told us to be known as His followers by our love for others.