I posted about this almost 10 years ago. Trump lies constantly. Almost every word out of his mouth is false. Hillary got caught slightly twisting the truth a couple of times and was branded a liar. Meanwhile, the MAGA ding-dongs swallowed a fountain of bullshit directly from Trump’s mouth, nodded along and just said “Aw, that’s just Trump being Trump.”
My theory is it’s about expectations and predictability. If someone always lies, then you can trust what they say to be a lie. Your brain doesn’t have to get off its lazy ass and evaluate the merits of their most recent claim. It’s a lie like everything else this guy says. You mistake consistency for credibility. And if you like the lie, you can decide to believe it. Because your brain is just on autopilot anyway—your critical thinking never had to kick in to evaluate the credibility of this claim (because it knew from past experience that it was almost certainly false), so no need to fire it up at the “Should I agree?” part of the process.
On the other hand, with someone who only lies occasionally and strategically, you’re always guessing. You know that any claim could be true or could be a lie, but there’s not an easy pattern to apply as a mental shortcut. So every time you listen to the occasional liar, your brain is firing on all cylinders in critical thinking mode. It’s exhausting and it leaves you with the feeling that you always have to be skeptical of anything that person says. They can’t be trusted. Not only because they might occasionally lie, but also because they typically tell the truth. And you have to work hard to sort the rare lies from the status quo of truth.