Life itself is nothing more than a collection of anecdotes. Outside of math and philosophy, all our knowledge is based on anecdotal/empirical evidence. And in terms of psychology in particular, "everyone", "always", "never" and "nobody" aren't really terms you should use. I never said everyone with red hair is insane or something, I just said a large amount of people with bright red dyed hair seem to have issues. It's a red flag to keep out for.

Now the question is, how deeply did you know all the people sporting bright hair colours, and can you be sure for real that most of them had no traumas they were dealing with? Someone being "reasonable" doesn't mean they're healthy. Nor does having mental health issues mean you have to be unreasonable or even unpleasant.