Doesn't everyone have those? Like, I'm unlikely to really engage with someone about my health unless they're a doctor or otherwise have some area of expertise. Or if it's just a casual, friendly conversation, to kill some time.
Everyone has biases. But you aren't describing a bias, you are describing a refusal to engage with people below you. Speak for yourself, I don't have that.
We’re all humans and life is very complicated with many facets. If we all looked hard enough I’m sure we could find a person you’d refuse to engage in a debate with over their “thing.”
But that wouldn’t be a wise use of time in my opinion. And that’s what they’re ultimately driving at: we all have limited time to expend, so do it in things that matter to you. I believe “matters to you” is a bias.
"Below you" is a bit of an exaggeration, I think. I said that I might think less of someone as a software engineer if they express an opinion that I think is particularly bad. Hardly egregious, in my opinion. I also might not - it frankly depends a lot on the situation.