He listed several beliefs in the article on topics liberals love to believe in -- abortion, gender issues, gun control, government intervention to save the world from climate change, etc.
Let's take abortion, for example. Pro-choice people frequently say a fetus is just a "clump of cells" as if a fetus really doesn't have a completely separate body, DNA, lungs, arms, legs, eyes, brain, heart. They disbelieve scientific facts because they desperately want to believe that a fetus IS just a clump of cells.
Then gun control -- I'd say most liberals believe that strict gun control will reduce gun-related deaths. But the facts have shown that in places where there already IS strict gun control, gun-related deaths are out of control. But they still believe that gun control will work -- their beliefs aren't based on facts, but their desire for it to be true.