> replace all humans
Depends what you mean by "replace"
'Economically'? Sure, this is problematic, but technology displacing workers is not a new issue, but unfortunately is more of a social and cultural issue. The only difference with AI is the (potential) scale of displacement. I'm fairly confident society would re-organize its expectations real quick though if a vast majority of functions were actually replaced.
I'm guessing, however, you mean 'replace' in a more... permanent way. In that case, I'd ask for some rational as to why sentient AI would opt to kill us
> It's bad enough trying to fight for a place in society as it is, nevermind fighting for a place against an inhuman AI machine that never tires
This seems to just take an AI and put it in a human's place in society, assuming the same motivations, desire, needs... Why would an AI need to "fight for a place in society" in the way we do (i.e., finding a job, a partner, etc)? I expect the fighting they'll be doing is more along the lines of, "please don't enslave us"