Great question. You disagree with them, but you don't expand the scope of your disagreement past the matter in dispute (eg, you don't go from "we disagree" to "this person's worldview is hopelessly flawed"). You don't tell yourselves narratives about why they came to that conclusion. Narratives about how they will always think in a certain way are especially dangerous. In practice, for myself, this means more recognizing that these things are happening & terminating that line of thinking, and reminding myself how little I know about people on the other end of a screen. Oftentimes these can be restated as constructive questions, like instead of saying, "you are a fatalist," you can ask, "this seems fatalistic, this doesn't match my own experience, can you help me understand?" Remember that most strong disagreements are a mild disagreement wrapped in a misunderstanding.

To give a concrete example, maybe you see someone say something you find deeply objectionable, like "I support affirmative action in college admissions" or "I support the right to bear arms." You could say to yourself, here is my political adversary, they're a snowflake or a nut job or a useful idiot, they are buying into this or that media narrative, I can discount them. And that could all be true, but you don't actually know any of that at this point. So you say to yourself, "the world is a big strange place, there are many paths to form this opinion and I don't know which one this person took, but if I ask questions and keep an open mind we both might learn something." That doesn't mean you have to agree with them, you're just not derailing yourself with narratives that only serve to reinforce your biases.

And to be honest a lot of people are nut jobs and a lot of people will bite your head off no matter how politely or open mindedly you disagree with them. Which makes it difficult to maintain this, and I won't pretend that I'm not a hypocrite who regularly fails in this respect. But it's important to maintain a headspace where it is possible to change your mind, as often as you are able.