Critical thinking is encouraged by noticing and thinking through counterfactuals - things which are a certain way, but which might have been another way. Lots of very unpleasant things have persisted as a consequence of people NOT entertaining counterfactuals; that status quo bias, or "that's just the way it is" is a refrain from someone who doesn't want to be troubled by something immoral that survives by dint of cultural inertia. Richard Dawkins has referred to this as "the anesthesia of the familiar".
Recently I found myself wondering why Catholic priests were celibate (and many other Christian priests are not), and if it had always been this way. An article that became popular on Reddit due to a saucy quote from Martin Luther (see below) answers the question. It seems that the adoption of priestly celibacy was mostly a political attempt to keep the priest class from accumulating more power through inheritance. No legitimate kids, no land. It's just an old-school power struggle between political classes, and that's actually how the argument began in the 10th century. It had little to do with Paul and Christ remaining single. A thousand years had transpired before this policy was adopted.
And that quote from Martin Luther? "To say it crudely but honestly, if it doesn't go into a woman, it goes into your shirt." (Note that in religion sexuality is usually viewed from a heterosexual male perspective; kind of a provincial viewpoint for the all-knowing supreme force of the universe to be taking.) After another five hundred years went by, people started thinking that masturbation was a bigger concern, and since the reformations were creating more decentralized churches, maybe the political powers weren't so concerned with priests' kids' inheritance.