(To preface my comments, I think I should let you know I'm coming from an agnostic/atheistic position; I think all religions are manmade.)

It's not entirely surprising that an "underdog" monotheistic religion would develop such a "policy" like that of the Shariah (regarding Murtids, agnostics, atheists, etc.).

>>>"I have no idea how to make sense out of this seemingly barbaric and horrible act. That is why, I need some comments here."

Christianity seems to have gone through a similar phase, at much the same point (timewise) in its development.