Well, honestly, you have to fight it. There is no easy answer. If you believe "A" then find people who think "A" is wrong and see why they think opposite you. Ignore the screeching extremists for the most part, but do occasionally check them out so you know what language they use. In the US we call certain phrases and words "Dog Whistles" so that the nut jobs know you are on their side, but no scaring away the moderates.
The point here is not to get you to change your worldview. The point of doing this is to get you to see your beliefs through the eyes of the opposition so that when you get outside your filter bubbles you can debate intelligently. Nothing disarms someone faster than saying that you read on THEIR media (talking point here).
That, and leaving your filter bubble will lessen the risks of you becoming an extremist yourself.