It is unfortunate flagging censors the posts. Was interested to get more context in the thread and instead it’s hidden entirely.
Regarding the rest, I’m happy to simply disagree with you having observed this in practice in other communities. It’s not black and white.
One thing to remember about online communities is that size is by far the most important factor. Things work very differently at different orders of magnitude. If you know of a community of HN's size or greater (millions of users a month) where snarky dismissals have helpful systemic effects, I'd like to know what it is, because I don't currently believe that's possible.
As for flagging, what thread are you referring to?
In a context like this, snark doesn't encourage people to "go do their own research" or save "impressionable / gullibile minds", nor is that really what people care about. (If it were, they'd expend energy doing those things in a way that might actually work.) Rather, its function is to vent one's own frustrations by translating them into concentrated language. The effect this has on community is to pollute it with fumes.
This is destructive of the ecosystem, unless one is happy with a single species, the snark, consuming all the others. Therefore we all need to find better ways of self-regulating and containing our frustrations. Then we can address other people in a way that has a chance of connecting with them.