|5.: Respect other peoples newssources.|
It is so tempting. Tell someone that you don't believe the newspaper they cited articles from, and the uncomfortably consistent argumentation they built up falls together, leaving you and your notion secure again.
Don't ever try that.
Discrediting a newssource requires more than that one article from three years ago that wasn't entirely correct, or an obvious political bias - you'll find few newssites without one. Accept that Leftys will often quote facts found on Salon.org, while Conservatives will cite FOX. Unless you can find contradicting factual data, you will have to accept the newssources validity and instead go the hard way, argumentatively tackling the points based upon those articles.