[corresation]

As others have said, the original title said "Hated expensive, crappy stock photos so I made this." So yeah, that's where he denigrated an entire industry.

and for some reason HN audience found it valuable and voted it to the front page

This a recurring retort. It's nonsense. A very small percentage of HNers can get something to the top of the front page (especially if it uses a title that panders to a bias, given that many people never actually click on the link). That they do in no world inoculates the target against any criticism.