I'll never understand how people can justify seeing the world in such binary terms. You don't honestly think someone is "bad" or "good" based on political ideology, do you?
It's easy to summarize the world in binary terms based on empirical evidence that comes from your own experiences. In my experience, conservatives are far more likely to back up their claims with evidence than those on the left. Is it always true? Of course not. But it certainly is a generalization I am convinced that is supported by reality.