I'm only an occasional poster here, but I answer questions all the time on Stack Overflow where belligerent newcomers are extremely common. It takes constant vigilance to avoid falling into "snarky expert" mode.
One thing I remind myself is the audience is a lot bigger than the person I'm responding to. It's okay if I can't get through to the OP. There are dozens or hundreds of other people reading my words. Seeing which posts get showered with hearts and which don't is a great reminder that it's not just the two of us.
Arguing reminds me of improv comedy. The first rule of improv is to say, "Yes, and..." rather than "No...". Meaning, try not to flatly contradict what someone is saying. I avoid replies full of "nos" and "sure, buts" like, "No, that won't work. It doesn't make any sense. Rust is not an object-oriented language..." It's a lot better to build off of what they said. "The way you wrote your code is what I would have written in Java or C#. Just so you know, Rust is a different beast. It takes a bit of a mindset shift because OOP isn't always the best way to express ideas. Code and data aren't as tightly coupled as in other languages, and inheritance isn't really a first-class concept. I might write your code like this..."
When I respond like that I find people don't argue back nearly as often. Why? Because I'm not arguing with them; I'm conversing with them. I didn't say their post makes no sense, that I don't even get what they're saying -- I do get what they're saying; it's totally understandable; I wrote my code the same way when I started with Rust; etc.