I have been known to describe certain people I know as “Often wrong but never uncertain.” It’s not a compliment.
Though I love someone who has the courage of their convictions, I find that allowing yourself to consider (and then re-consider) your opinions has value. The way I felt when I was 19 is not always the way I feel when I am 40. Nor should it be. But many people find an opinion (or a party, or a group, or whatever) that they side with and then never re-consider. They cling to the same ideology regardless of what is in front of them.
One of the best ways to really re-evaluate is to listen (REALLY listen) to the other side of an argument. What is their perspective? What do they know that I don’t know? Why do they feel the way they do?
You might change your mind. Or you might not. But then you would really know.