We tend to polarize things. Picking a side and sticking to it is our natural instinct. Our ancestors didn't have much other choices, it was either kill or be killed, eat or starve... Them versus us.
It's more efficient to divide things into just two different sides. Everything else in between just makes things too complicated. Back when our survival depended on quick decisions ot was vital to recognize the danger.
Even if our choices are way more complex today we haven't evolved as much to handle such variety of choices. We still make quick decisions between things and stick to it ever since (or end up in analysis paralysis).
It's hard to fight this nature of duality. Even if you know about it and try to keep away from absolutes the divides are endless. And even if you would get rid of such duality you would just end up being one of those against everyone else who's not.