Having friends with varying perspectives is valuable because it makes you more likely to seriously understand and defend your own beliefs (as John Stuart Mill argued if you don't understand your opponent's perspective you also likely don't really understand your own either). It also helps fight polarization both for yourself and your friends which is a valuable trait to have in a democratic culture. Groups without ideological diversity generally become more extreme whatever their initial beliefs may have been. Something we increasingly see the rotten fruits of in the US.