John Oliver returned to HBO Sunday for a new season of "Last Week Tonight" and immediately got to work on keeping President Donald Trump in check.

"Trump has made it clear that reality is not important to him... How did we get a pathological liar in the White House?" Oliver asked. "Where are his lies coming from? Why do so many people believe him? And what can we possibly do about it?"

Citing reasons that Trump's more reliant on what are widely considered unreliable news outlets, such as Infowars and Breitbart, Oliver said, "He also takes information in from frighteningly unreliable sources such as Breitbart, the organization which gave us Steve Bannon -- now Trump's chief strategist."

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The comedian continued: "Breitbart has published such Pulitzer-eligible stories as 'Birth Control Makes Women Unattractive and Crazy,' 'Racist, Pro-Nazi roots of Planned Parenthood Revealed,' and 'Hoist It High and Proud: The Confederate Flag Proclaims a Glorious Heritage.' You know, the kind of headlines you see your old high school friends share on Facebook and think, 'Oh, that's a shame! I guess Greg sucks now.'"

Oliver noted that a frightening level of camaraderie even exists between Trump and Infowars' head honcho Alex Jones, who at his worst claimed that the horrific Sandy Hook school mass shooting was a hoax.

Trump appeared on Jones' show while campaigning and praised the conspiracy theorist. "Your reputation is amazing," Trump said. "I will not let you down, and you'll be very, very impressed -- I hope."

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The late-night host also demonstrated how dangerous Trump's essential game of socio-political "Telephone" is to the American public. "This is really dangerous because there is a pattern here: Trump sees something that jibes with his worldview, doesn't check it, half-remembers it, and then passes it on, at which point it takes on a life of its own and appears to validate itself."

Oliver closed his diatribe against the president with a stern warning: "We all need to commit to defending the reality of facts, but it's going to take work."

See Daily Beast Marlow Stern's take on Sunday night's show below.

0209_launch_critics_1View GalleryGetty Images37 of Donald Trump's Loudest Critics and Supporters

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