Has nothing to do with athiesm. It may have more to do with people and culture however cruel it may be. A billion people under a communist regime where people don't count for much may cause that sort of mentality.
How many so called god believers did horrible crimes during war? When there is an opportunity to do so, there are people that will do it. If the attitude is such that another human being isn't worth a lot, who will care? In this instance it many be cultural. After all, how many of those countries have young girls sold to brothels or as slaves because parents can't afford to keep them. We, in the west have a good life and this videois shocking to us, but is it possible that these things happen more often than we think in third world and developing nations except they aren't caught on video or if they are they're not released to the public?
We are living in one of the most peaceful, most developed nations on the planet using and abusing the most resoures of any generation during human history. Our culture is totally ignorant of many other cultures and the value of human life in those areas.