I think it's to do with the iPhone. I noticed this a long time ago on HN: any comment that could be interpreted as negative towards the iPhone was downvoted. Like you, I couldn't understand it at first, but eventually concluded it was because of things like describing the iPhone as "underpowered" (compared to a desktop), even in a neutral, factual, discussing-the-engineering sense.

My solution is to avoid iPhone-related threads or to not take them seriously, and to not comment in them (or if I must, to stress the iPhone positives explicitly). No, it's not a great solution.

EDIT as predicted, this post got a downvote.