Is it true that 'nice' professors fail to produce good students? This is a very tough question to ask because there are so many advisors on this forum so I am expecting most inputs from the current grads. This question largely stemmed from a post I read online about picking advisors.

The top recommendation offered on a list of things about picking supervisor is to never pick someone who is nice, friendly and available. Specific examples being "nice associate professor ladies" and "prof emeritus". 

This quote caught my attention the most


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


But this is just one person's opinion. So my question is to what extent does this idea actually hold in academia? Is there any truth to nice profs are less capable than mean profs in producing 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.