I'm only 24, but I've read a lot of books in my young life, some of which I'm sure it would surprise people to know I've read. If you know me personally, you know I'm pretty left of liberal and I scorn any religion that discriminates against any group of people, so it might surprise people to know that I've read several Ayn Rand books and I've read several books on fundamentalist Christianity.
Why? Why would I read books about things against my personal values? Why would I spend time reading things that are in no way aligned with my personal beliefs or morality? And furthermore, shouldn't I be ashamed at having read these things? Let's dive a little deeper.
Far too often I've heard people write off other people or groups with whom they disagree as just being "crazy," as though some faulty mental faculty is the explanation of all the reasons why these people or groups can't come to reason and align themselves with the questioning party. This is true no matter what side you're on--I've heard conservatives and liberals call each other crazy and I've heard religious and non-religious call each other crazy. I'd argue that "crazy"-calling is a pretty universal phenomenon.
But what I've found is that simply writing someone off as "crazy" isn't helpful to gaining an understanding of those with whom you disagree or a deeper understanding of your own beliefs. It's not enough to know what you or someone else believes if you can't properly articulate the larger why behind the belief. I've realized that calling someone "crazy" isn't productive and does little to generate dialogue. "Crazy"-calling, it seems to me, is merely a colloquial way of shutting down a conversation about something that is not deemed worthy of actually explaining.
I know what you're thinking, "But some people really are crazy! Just look at XYZ!" and if our perspectives are similar, I'm likely inclined to agree--I won't pretend that I've turned away from calling people "crazy" as popular language is wont to do.
But I tend to look at the world as a whole like this: everyone lives within their own bubble of reason. Everyone has life experiences and influences that contribute to their worldview; in short, the way each person processes information is entirely relative.
This means that each person can think and believe things that, to them, operate on the basis of logic that's established by their worldview. Humans, being selfish animals by our nature, are concerned with survival and we won't do things unless we believe them to be helpful to our survival even if, in reality, they're not.
But one's worldview, being relative as it is, isn't necessarily based in reality. With each person's relative bubble of reason, some operate within the context of the greater world logic (i.e., what is universally true based on solid, non-subjective facts), some operate tangentially to the greater world logic, and others operate completely outside of it. That's how you can have people that can rationalize their beliefs according to their worldview and operate on a basis of logic inherent to their worldview, but not necessarily operate within facts, reason, and reality.
Even more important to note is that understanding someone's worldview and beliefs does not mean that you agree with them. I've read Anthem, The Fountainhead, and Atlas Shrugged by Ayn Rand despite not agreeing with her capitalistic views. I've read Radical by David Platt and The Christian Atheist by Craig Groeschel despite being a real Atheist (the type he's referring to aren't). Do these things shock you? They shouldn't.
While I have no intention of making considerable reading progress into a canon of literature about things of which I don't agree--I find that would be unproductive toward my reading goals and personal development--I do think occasionally reading something that you don't agree with generally makes you a smarter, more well-rounded person. And if you're confident in your beliefs, you have no reason to fear the reading will cause any change in them.
That's why there's no need to be shocked when you find out someone has read something that seems fundamentally opposed to the person you know them to be. There's nothing wrong with them--they're exploring the depths within themselves and know that understanding is not agreeing.