That is a question asked by normal people about people who do terrible things.
How do they live with themselves? How can they sleep at night?
I always say "they sleep just fine". They are convinced they are right and just and have no trouble sleeping.
Now, via Instapundit, a bit of insight confirming that thought.
"Jon Moulton, one of London's most successful venture capitalists, agrees. In a recent interview with the Financial Times, he lists determination, curiosity and insensitivity as his three most valuable character traits. No prizes for guessing the first two. But insensitivity? The great thing
about insensitivity, Moulton explains, is that “it lets you sleep when others can't.”