Have you ever studied the 10 plagues visited against the Egyptians for their slavery of the Jewish people?
You mean the fable? The fantastical mythological, supernatural narrative spun by religious authorities in support of their world view? Yeah, that's hard to miss.
Especially the slaughter of every first-born Egyptian child?
What about it? Are you saying that because a tyrant slaughtered a bunch of kids thousands of years ago, that therefore a crazy Islamist and his brother might be excused for blowing the guts out a kid standing next to one of their planted bombs?
The list goes on and on. I'm afraid that slaughtering children for religious sacrifice, even innocent children to teach their parents a lesson, as a long cultural history.
So does hunting down rival tribe members, killing, cooking, and eating them, in some ancient cultures. So?
That doesn't make it "rational", but it's certainly historically well founded.
Well founded? The moral foundation for that sort of stuff couldn't be shakier. It's based on magical thinking routed in ignorance.