People do seek out the information which confirms their world view, but people also can really be changed by exposure to information. Read accounts of racists who have reformed. It's always the same story. Their beliefs were slowly chipped away by exposure to information and (most importantly) a diverse group of people. They spend time with one person who doesn't conform to their prejudices and then another and eventually it clicks for them.

Right, but what about the people who don't reform? Are they somehow not exposed to all the same stuff as somebody who does reform?

Well, yeah. A lot of racists never get to know the people they claim to hate as actual people or even interact with them beyond the most superficial encounters (passing one on the street, having one hand them change change at the store, etc). They even tend to stick to media which leaves them comfortable in their world view. Getting them out of their comfort zone is crucial for change (likely true for everyone really). Not everyone will change either. There are some remarkably stubborn people, but the only chance any of them have involves them being confronted with information outside of the narrow echo chamber they live in.