It's not surprising or new to me. That particular strand of behavioural psychology was asked and answered a while ago. There's no doubt that there are some liberal wankers that love to get on their moral high ground and seem to totally dismiss the fact that they're biased and demonstrably wrong about a great many things.
To paint that as a particular ailment of "the left" is pretty fecking stupid though, in my view. Particularly when you're resorting to using an article which is so heavily partisan, with palpable anger at the other side dripping off the page, and then describing that as news.
You're criticising people for living in echo chambers and then reverting back to one of the echo chambers you're particularly fond of, for obvious reasons. It kind of ruins your entire point.
At the end of the day, the demographics that voted for/against Trump will tell you quite conclusively that those against are better educated and better able to apply critical thinking. Across people of similar demographics on both sides of the political spectrum, they are equally prone to seek out echo chambers, and equally prone to bias.
Are any side more likely to be ignorant of their own biases? I've not seen any evidence to suggest that, beyond baseless partisan commentary and anecdotal evidence from the "news" article you provided.
Even if you don't have the evidence, I'd be interested to hear your hypothesis on why "the left" are more likely to believe their own bullshit when everything points to the split growing on both sides, with heavily partisan media playing a pivotal role in growing that ignorance and disdain on both sides.