I remember reading a book one time, a novel that really has nothing to do with this question, other than this one scene; A military experiment goes awry, the psychopaths on whom the experiment was being conducted vanish into the general population, and what does the man conducting the experiments say? "There must be 50,000 murders and rapes a week in this country, 300 a day. What's 50 more?"
Joseph Stalin (undoubtedly one of history's most evil men) put it this way; "When one person dies, it's a tragedy. When thousands die, it's statistics."
I don't think that people can unwittingly commit an evil act, not unless they were manipulated into doing so, and were lied to about the consequences. In that case, such a person is yet another victim of an evil person's crimes. The truly evil people are those who use statistics to justify murder. And then, there are still others who simply do not care about hurting others. They do it just for fun.
In the end, the people who do evil and know it do far more evil than the people who don't know they are doing evil. In fact, the latter group is probably being manipulated by the first group into doing what they are doing.