For the same reason that the left fears stability. One side is about change, the other is about being static. The idea of Right and Left have been (until the last 30 years or so) a balance between the two -- the pendulum swings one way and then the other. Nowadays it has to be one way or the other. I'm surprised there hasn't been more violence.

It’s like giving them homework. Once they knew the rules, now they don’t. Once they knew how to intimidate, now they’re intimidated by what they don’t know…

Unless they are white upper class they don't like them

After much reading and thinking, I've finally concluded it's because:

Humans are genetically programmed to be conservatives and fear new things. This is a holdover from our evolution as small tribal hunting bands where any stranger was likely to be a threat (except, significantly, a female, who was a potential breeding partner as far as males were concerned). It takes a conscious effort of self-education and self-programming to overcome this instinctive fear of new people and things.

Different is bad. People that are the same as you are safe.