What is that supposed to prove? That those news sources don't have a liberal bias?
You completely missed his point. He was talking about that "e-word" you despise so much:
evidence.
IOW, if one wants to claim that ABC, CBS, CNN, NBC, or NPR are "far left", then it is incumbent on one to provide examples to support that claim (AKA "evidence").
IOW, if you make a claim, you need to be able to back up that claim.
A simple concept, really, and one that you will encounter all the time in geology.