I think of it as a purity test. If one is willing to accept obviously absurd and contradictory material without evidence, (they call this faith,) it means they are just the sort of uncritical person that's likely to go with the program without pushing back. It's like how the Nigerian prince e-mail scammers intentionally include grammatical and spelling errors, because the people who overlook that and reply anyway are far more likely to be successfully scammed.
Each religion has a slightly different flavor of absurdity. They all rely on indoctrination and a lack of critical thought to persist. They all have the capacity to become extremist and frequently do. It's only a matter of time until the men who claim to speak for god(s) say their god(s) want violence.
While extremism isn't limited to Abrahamic religions, the story of Abraham, the one they all have in common, is a pretty fucked up story. The moral is: if you hear voices that tell you to kill your son, you should do it without question because that's definitely God testing you. That's a dangerous lesson to teach children, some of whom will grow up to be schizophrenic.