It depends on your sources, I suppose. Can horrendous crimes be carried out by atheists? Of course. Then again, horrendous crimes can be carried out by anyone, irrespective of their religious (or lack thereof) beliefs. There have been many crimes committed by those who have attended Church, prayed in mosques and who worship God in various means. I have to draw into question then, the idea Paul is hinting at, namely that atheists lack morality. Some do, some don’t, much like followers of the world’s religions.