Liberal doesn't mean smart. Leftists can follow an idiot into a foolish war just as conservatives can.
The liberal slant to the media is based on the many assumptions and conceits you see in every day news reporting: that the government has a greater control over trade and economic activity than it actually does, that the government needs/should have an automatic and direct role in alleviating any social problem society encounters, that people in poverty should never be critically questioned as to how they arrived in that circumstance, that consumerism is greater than capitalism, and that identity politics trumps self-determination.