Well, the fear that AI would want to eliminate us comes from several lines of thought. First and foremost, it's about ensuring our survival which is literally hard coded into every living being.
Then, there is a second line of thought that says that AI may make a logical conclusion that everything that is wrong with the planet Earth is because of us humans.
Likewise there are many other reasonings but I think at the end of the day, the discussions happen because we don't want one of our creations to be the reason of our end. I think it's just for precautionary measures.
Well... humans are responsible for the damage to the planet. But, I think , when they realize that, they are going to teach and help us to heal and preserve earth.
I hope, when this time comes, they are going to preserve our lives not exterminate us. After all, humans are unique and we create them.