Why do US liberals consider anything remotely not in line with their ideology right wing / alt right? Why can't opinions exist on a spectrum?

I ask about US specifically because in Sweden where I'm from I would not be considered right wing. I used to consider myself left, but have moved more toward the middle in the last few years. Mainly because I really value things like free speech, which to me is not a right wing idea. But nowadays it seems like it is. I hate the fact that I'm now lumped into this right wing category by people on the left. I'm not right wing / alt right, I'm in the middle. Why is there's no nuance anymore? Seeing the world as black and white is harmful, it pits people against each other. So why do US liberals feel the need to lump me into this category when I'm not even right wing?