Shayma Ali, 36, who was suffering from psychosis, stabbed the four-year-old up to 40 times and took out her liver...."...a voice told me 'if you love Allah you should sacrifice your daughter."'
I'm not going to jump on this as an example of the religious causing harm, as I'm sure many critics of atheists might think we'd do.
Instead, this is the primarily danger of psychosis. I don't think I'd do this, but I can understand. perhaps better than others, the motivation for doing it.. One possible issue, in my opinion, is that this woman didn't adequately defend herself against erroneous thought patterns ahead of time. She believed in Allah based on no evidence, she believed in Djinn on no evidence (probably, like other Muslims I have spoken to, she relied on stories about a neighbour of an Uncle who met a Djinn or some such. I've not met a Muslim who did not believe in Djinn).
Believing in things without evidence doesn't necessarily lead to harm, but dropping critical thinking in areas where the stakes are as high as they often are in religion, you open yourself up to doing terrible things under the influence of sudden onset mental health issues. 5% of people will suffer a psychotic episode in their lives. That sounds small, but when we realize that this means 1 in 20 of us, it may well drive it home as quite a common thing.
So much of the evidence in favour of Allah, Yahweh and Jesus etc is based around 'personal relationships', 'personal religious experiences' and so on. Is it any wonder that people that hear voices sometimes attribute them to these characters. After all, what else are people that say they have experienced the loving presence of God doing?
And this is why I have adopted a skeptical position. I know I occasionally believe weird things, but if any belief that I hold that is life-and-death important, I run through the skeptical mill before acting. Any belief, I insist to myself, is subject to change based on further information.
Does this render me immune from committing a terrible act? To be honest, I don't know. How could I know? I suspect that a powerful psychotic break could occur and my critical reasoning will be irrelevant for that time. That said, I've heard voices and they have told me to do terrible things. Fortunately I know the human mind can play tricks on you and this is always the evidentially supported hypothesis and thus the preferred one over unverifiable theories about commands from supreme beings.