I think you're taking the meaning too far. It's not that someone in a bad position is not allowed to feel bad. Rather, you have to consider the context in each case. A friend could be having a hard time, and even if your situation is technically worse, that doesn't invalidate theirs. Because if you are willing to invalidate your friend's difficulties, by that same token you could say your own are invalidated by those in an even worse position than yours.

Essentially I'm saying that everyone's life is different and their worries are valid. Yes, perhaps it can be a touch tone-deaf for one person in a privileged position to complain about something relatively trivial. But for someone to assert that their situation is infinitely more important, and that their friend shouldn't be allowed to complain about their own experiences... it reeks of envy and narcissism.