It's more about how they tell other people that they might be on the wrong track. It's not good to be oblivious of mental illnesses. But if they have nothing but scolding and derision and no solutions, they should rather shut up.
Also, I hate people who think that if something works for them it must work for everyone else and if you don't do it their way, you do something wrong. People who tell you how you should eat, how to dress and always tell you "oh, it's not how you do that. You must do it this way." 🙄