To say it is God's fault that millions of people have died in His name at the hands of people who were using His name to justify their sin, is the same as having someone steal your credit card, use it to run up charges in my store in your name and then not pay those charges and I become critical of you because it was in your name that they were charging. It's the same thing because you are holding God responsible for the actions of others rather than holding them accountable for their actions.