On the internet, people are far too quick do this because they can't imagine that views which seem (to them) so wrong and dumb could possibly be coming from others in good faith. But the truth is that the opinion diversity of the community wildly exceeds intuitive estimates. The null hypothesis, therefore, when it feels like astroturfing simply must be going on, is that you're underestimating the good faith of others. It's super tempting to reach for the stick (PR! astroturf! shill! how much are they paying you!) but we know from experience that this degrades discussion quickly, and therefore the temptation needs resisting—hence that guideline. Real astroturfing exists, of course, but it's a quite different species than this common astroturfy warbler. If you're worried about it, we can investigate, but you need to email us rather than post comments about it.
In this case Occam is even more active than usual because there's a particularly obvious explanation for what you're seeing: the tendency of the community to respond with objections to whatever gets posted. If the article were slanted the opposite way, so would the comments be, not because different 'astroturfers' would show up but because the people most motivated to comment are the ones who see something to pick holes in. Then others show up to pick holes in the way the first round of holes was picked—invariably leading with "I can't believe this community is so X", not realizing that they're motivated by just the same thing as their predecessors. This dynamic is a problem in its own right but for different reasons.
Btw your assessment of HN as 'right wing' has the same cognitive bias—underestimating the diversity of the community—embedded in it. It's clear (painfully clear, at least to me!) that the opposite wing sees HN just the opposite way and has just as ready a supply of examples to point to. An anarcho-anti-capitalist story has spent the last several hours on the front page, etc.