I'm not sure it's really a bashing. I read it as he's glad after all that facebook didn't hire him, so it's more like a message for those who already "lost" or will "lose" in puzzle-based hiring process. A message that states it's not necessarily their (i.e. prospective employees) loss in the end, and the more important part that it's not a reason they should feel bad about themselves after such "loss", because solving riddles is about solving riddles and not about finding good programmers (being one doesn't necessarily exclude having puzzle-solving ability, but it's not like a symmetric difference of these sets is empty, really, more like quite voluminous, I would say).

Why not? I don't think it's healthful for a culture to impose a wide penalty on criticism.

Criticism, if constructive, is not 100% negative. The post indeed criticizes Facebook, but also lays down an explanation of why Facebook's hiring practices are wrong. It contains useful information.

I agree completely. This could have been written in a way criticizing the hiring practices of companies where it didn't come off as a complete bashing.

One thing you need to remember is that technical people that are performing phone screens are going to do a little research on you as a future candidate, and this isn't the first impression you want to make when vying for a job.