I think I can answer that, because I’ve thought about dangerous hair before. In cartoons and anime, blue hair is often seen as a mark that sets a character apart, they are often the intelligent archetype, or perhaps the super talented type. They are marked as different and unique, their hair makes them stand out and everyone knows when they see blue hair that this means that this character is probably special in some way.
Dangerously deluded land whales (and, admittedly, others) see this, recognize it in their hindbrains, and want that “specialty” for themselves. They want to be the ones who stand out as smart and talented, they want to be the ones where just one look immediately identifies them as “the special one”. The problem is that, as I said before, they are dangerously deluded, and so what really happens is that they immediately mark themselves as someone to avoid, because their narcissistic desire to be visually different and “special” has made them forget that the reality is it’s not a cartoon or an anime and all they’re really doing is making it obvious to the viewers that they’re crazy.