Exactly. That's my point. It is true that sometimes an idea is too stupid to even deserve a reply. But simply stating here that 'this is so dumb, I'm not going to respond to it' doesn't contribute anything nor is it in line with the spirit of HN, per https://news.ycombinator.com/newsguidelines.html

The problem with what you're advocating every idea or comment either have a reasonably in-depth response or none at all. That reduces the poster's toolbox and lets the naive observer think the fundamentally unsupportable ideas might not be being noticed.

A reply that says "this is obviously wrong" may seem contentless but it's just "minimal content". You should be able to respond like this for the same reason you should be able to down vote things without comment. It's like a professor giving comment on an exam. Some questions they will just mark wrong, some they might write "makes no sense" to get the person thinking or clarifying and others they'd go into detail with.

What you just wrote is just so wrong that only a complete fool would waste their time engaging with you. Do you really believe that the previous sentence is a worthwhile contribution?

There was literally zero argument in the original post. You don't have to write a full analysis of everything that was said, you can just pick the parts you're willing to discuss and focus your attention on that or don't engage at all.