I've just finished a book written by an author whose views on many subjects differ from my own. This should be an altogether uncontroversial proposition.
If every book I read is a regurgitation of my own ideas or ideas I've read about and agree with in other books, I am unlikely to expand my own mind. I believe it's important to expose one's self to a wide range of thoughts and perspectives because one's view of the world is enhanced when it is formed not merely by the limited experiences available to any single person but also through visiting a broad scope of ideas.
My capacities for understanding are greatly enhance when I engage with differing ideas—not only my understanding of others' thinking but also my own. I can better recognize my blind spots and biases... and where I should pursue further insight. I grow in my ability to recognize how perspective is formed and whom may be more likely to hold specific vantage points.
We live in a time when it is increasingly seen as inappropriate or unnecessary to read the works of authors who hold varying and even opposing views to your own; but I say that when we read, we are less engaging with the author than we are with the text—and to cut one's self off from a textual perspective merely because of ad hominem concerns is to further dim the lights of one's own perspectives.
The read I've just completed doesn't dismiss my thoughts; rather, it enriches them. I am not threatened to know that there are ideas out there that run in some way counter to my own. I am informed by it.