Whoa: No one's saying unattractive or fat or dirty people are inherently evil or that blank stares mean blank souls.
Listen, IMO, appearances of killers or people who do horrific things are very, very important. I have been taught since I was small to use and hone my powers of observation. IMO, everyone should.
There is, often, a common "look" or similarities in expression, to people who do things like this. There is, often, a common look or similarities in expression to people who are evil or people who have suffered a psychotic break, have been brainwashed or whatever. I think conversation about that look is important because if you can catalogue it and file it away, if you ever notice that look in a family member or friend who is suddenly acting differently or in a stranger who is acting oddly, you may be able to do something that could save yourself or the person you know.
I can't say if this person is sane or not, or just evil, but something in his eyes and smile looks a bit like Jared Loughner to me.
Does that mean that everyone who suffers from a mental issue has a look? Of course not. Does that mean that "normal"-looking people can't be killers, or can't be evil? Of course not. But appearances can tell us a lot. And those trained in observation, like the Israeli forces at the airport and air marshals, well know that.