Just a guess, but you're probably getting down voted because your opinion is senselessly cruel and offensive.

Imagine if people with your color hair were suddenly considered weak and shameful. You could dye it, of course, but lets say for the sake of argument that hair dye is needlessly complicated by conflicting scientific information and multi-billion dollar industries fighting to get their share of your dye dollars.

Now imagine that people look at you differently, treat you differently, and occasionally, reveal enough of their inner asshole to actually smirk at you in public for having the wrong color hair. You'd probably feel pretty helpless. No one ever taught you how to dye hair, right? Your parents stubbornly insisted that you were beautiful just the way you were, even though the kids at school called you 'brownie' and 'shit-hair' for being a brunette. You're undoubtedly confused, because having brown hair shouldn't affect the way people treat you, shouldn't make your opinion less valid, shouldn't be directly related to your chances at finding a happy, healthy, supportive relationship with someone who loves you for you.

So what are you going to do? You're going to eventually break down and try to find a way to power through and dye your hair, right? Hope that you don't mess up and draw even more attention to your hair problem? Maybe injure yourself so everyone can see how badly you've failed?

Of course you are, because it absolutely fucking sucks to sitting on the outside of an entire society. People loathe you, and the kindest of strangers only try to hide it.

Then, you're standing in the dye aisle and you see lots of buzzwords you don't understand like "semi-permanent", "volumes of developers", "tri-color", "hair color filler", "lift", and "lowlights".

Now you could probably understand the dictionary definition of some of those words, but this is a special context, okay? What does semi-permanent mean in the context of hair coloring? It takes a few months to grow new hair, so maybe semi-permanent is half that? Or is it shorter? Maybe a few weeks? A month? Who the fuck knows, because you sure don't. And you're a 'brownie', a 'shit-hair', so of course you can't ask anyone. That just gives them an excuse to sneer at you for not knowing. So you go home and cry and put off learning to dye your hair for another six months.

In conclusion, people are down voting you because you deserve it.