An interest in politics is important for lots of reasons. We want people interested, because interest often leads to participation and that ultimate of participatory acts -- voting.
People engage with politics in one of two ways, either through the media or through discussions with others. A study in the current issue of Public Opinion Quarterly asks whether exposure to cross-cutting information (stuff you disagree with) via interpersonal and mass media can influence political interest. The answer? Disagreeing with people can reduce political interest as "divergent viewpoints entail additional negative personal cost for disagreeing individuals." Exposure to plural media, however, increases political interest and engagement. In simpler terms, we can handle news we disagree with if it's in the media, but in real live people it reduces our interest in politics.
Of course, lots of people tend to hang out with people much like themselves, so how often they're exposed to cross-cutting political information is another question.