I've never encountered any form of bullying or discrimination in my 15 years academic career (in three different countries).
What I witnessed a few times though where post-docs that just got disinterested in their work and unproductive for months. It's not uncommon for post-docs spending months looking for their next job, and usually, their advisors are fine with that. They understand well the difficulties of their students or post-docs.
Academia is hard because it's extremely competitive, not because professors are some kind of bullies harassing their students. I'm certain it exists but it's far from the norm.
It's competitive because you're competing with the whole world, and there are some people out there who are much smarter than you. And you are constantly reminded of this fact, when you go to a conference (or because you don't get to go because your paper isn't accepted), when you read your colleague's paper and so on. I've worked with well-known people (including a Turing award recipient), and even them were insecure at times.
And of course, it's hard because you don't know if you'll find a job after your current post-doc. The more average you are, the more insecurity, the harder it gets.