When you are a child, the world is divided into two simple categories: people who you can and should trust completely, and people who you cannot trust at all.
As you grow older, you learn that the people you trust can make mistakes. If you are well-adjusted you keep loving them. Usually you realize that they are generally trustworthy but cannot be trusted to do certain things or make good decisions about certain topics.
It takes a lot longer to learn how to deal with outsiders. Our instincts are to judge anything that is done and said by the identity of the person. The childish mind wants to divide the world into good and bad people, and oppose anything that the 'bad' people do or say.
Maturity is realizing that 'good' people can make terrible mistakes and that 'bad' people can do good things and be a source of insight and wisdom. You start to judge actions and facts on their own merits.
The inspiration for this post was reading this quick article from Krugman. The man cannot be trusted to write rationally about politics, and if I were forced to make the categorization I would call him an 'enemy'. This does not change the fact that he is a good economist and often says valuable things about economic matters. This article is an example. It is wisdom and I should treat it as such, regardless of the identity of who said it.