I'm pretty sure there's literally no other topic on which the HN community is so overwhelmingly positive.

There are a lot of commenters here, so there will a bell curve (or some distribution) on any topic at all. Picking negative comments from a tail is always possible, but it misrepresents the community, in this case completely. Posting indignant comments about it just adds to the problem and takes the thread off topic.

What is it about software development that brings out these kinds of people?

Ive noticed it in any technical field. People love to hear themselves talk and miss out on a lot by not listening to others.

It's perfectly healthy to be critical. Depends how you do it.

>I find the level of criticism for SpaceX on this site to be incredible.

This has to be the funniest comment I have seen today. There are more than one post regarding this event with 300+ votes. Still the level of criticism for Spacex on this site is "incredible", Really?