And that's absolutely an argument I will support! and very much do care about.
It's just a fundamentally different argument to "Well clearly, arbitrary species A here at some arbitrary time B is the natural and morally right owner of these lands".
Were bears completely extinct in the area and reintroduced from elsewhere? If not, there's no arbitrary line being drawn whatsoever. It's currently bear habitat.
As long as this is not seen as justification to displace any other species just when we feel like it (because they probably displaced some other species), I can agree.
I can mostly agree with the rest of your points. But how many species are killing off thousands of other species in such a short time frame?