Sometimes it is difficult to understand and be tolerant of others who do things we consider wrong,evil or simply improper.  Our attitude is: we know how to behave, so they should also.  So when people do things we tend to judge them according to our understanding of right and wrong, proper and improper, good and evil.  
    If we are to be tolerant and understanding, we must recognize that while we all have many things in common, we are not identical.  We all have different genes, different upbringing, ate different food (which can affect the brain), had different teaches and different friends.  All of those things, and more, contribute to where we are know.  To expect the person in the lowest parts of the valley to see as far as the guy on top of the mountain would be ridiculous.  Likewise, to expect someone with a very different background to behave just like us.  So, to be tolerant of behavior we consider wrong, we have to understand that person is not starting from the same place we are.  This doesn't make evil or stupid behavior OK, it just means we show tolerance for those who do such things because they are not us and don't have the same understanding as us.