Compartmentalizing beliefs I think can explain at least some of this. Some beliefs, especially religious or political, people will often exclude from the scrutiny that they apply to other areas. For example, they will accept their religion that they likely grew up with, but will quickly point out that other religions are not believable, and usually for valid reasons.
It seems to me, that the beliefs that get compartmentalized are often ones we grew up with (I think that is why we see it so much with religion and politics). Lots of Republican voters grew up with a Republican family (same with Democrats). Most Catholics had Catholic family / parents, most Muslims had Muslim family / parents. These beliefs can become ingrained to the point most people don’t question them with scrutiny how they would if someone presented the idea / belief to them fresh as an adult.
I was just kinda watching the video in the background at work, so it is entirely possible I read the graph wrong, but didn’t having a really strong score in numeracy help overcome bias to an extent? I thought I saw a graph that had % getting the correct answer on the Y-axis, and numeracy ability on the X-Axis, with both conservatives and liberals having a trending line upwards as numeracy improved? Similar plots to the cream question for both conservative and liberal (in the case where the correct answer would conflict with their assumed beliefs), but shifted lower (which we’d assume was from bias). I’d re-watch, but You-Tube through T-Nation is glitchy to say the least. I had to refresh a few times just to get though it.