Is it true that 'nice' professors fail to produce good students?
That advice from the blog says to avoid an advisor who


  1.  Is nice, and friendly, and available.
  
  And never gives you the fierce criticism and the tough pushback that forces you to confront your weaknesses, take risks, stop whining, cut the excuses, get over your fears, and make hard decisions about reputation, money, and jobs.


It's the part beginning with "and never" that describes a problematic advisor, not the "nice, friendly, and available" part.

An advisor who is unwilling to criticize a student and share harsh truths when necessary is certainly problematic for many students. But I wouldn't necessarily conflate that with being "nice." For most students, an advisor who is genuinely nice is a good thing.

As for


  If you’ve never cried before, during, or after a meeting with your advisor, something is amiss.


Doing a PhD is difficult and sometimes discouraging  for most people. My advisor is one of the nicest people I know, and I've walked out of his office on one or two occasions and gone off somewhere to cry. Not because he isn't nice, but because what I'm doing is difficult, and sometimes we have to have some very difficult and/or discouraging conversations.