When you read things you disagree with you understand your own position better.
Books are lighthouses for your worldview. Newspapers and magazines are GPS satellites. The internet is a laser rangefinder. Agree or disagree, care or don't care; reading teaches you about where you are in the landscape of ideas.
Some ideas are new-to-you and open up continents of thought you haven't explored. Other ideas conflict with things you know to be true; punt 'em.
Reading widely provides the raw material for combining existing ideas in interesting and potentially profitable ways. It's hard to connect the dots if there aren't any.
Reading widely helps you understand the gamut of opinion on any issue. When you understand all the angles, you might be able to help everyone win.
Avoid confirmation bias: If you only read things you already think it demonstrates insecurity. The slightest breeze could knock it over.
Avoid pig-headedness: If you're so confident in what you believe that nothing could sway you, that's another intellectual error, and it robs you of the advantages education can provide.
New ideas are scary. Invite them in. Entertain them. Test them every way you can. Keep the good ones. Changing your mind when better ideas come along is how we get better as individuals and as a society.
Read widely. Read thoughtfully. If you don't think for yourself, someone else will do it for you, and they might not have your best interests at heart.