Most people are staunch partisans, above all else. If you do anything to challenge the black and white, team-based nature of politics, it is seen as a personal attack against their fundamental beliefs. It's why moderates or centrists receive a double helping of scorn from each party. The only thing more threatening to a Democrat than a Republican, is someone who challenges their two-party oligarchy.
Maybe fifteen years back Jon Stewart pointed out that politics is dominated by extremists because most people have better shit to do with their time. I think it's fair to say that most people are disinterested above all else. The people who are interested are generally interested tribally - it's rare you find someone who likes to watch sports but has no favorite teams.
So, it wasn't that people's policies were extremist but their views on things? That makes sense, now that I think about it. Many people of both parties (haven't seen much Dems, though) are utterly stubborn about the way things are supposed to be done all around the board.