Avatar does speak a little bit of truth, as far as I'm concerned. It's that any revolution against capitalism worth its salt will have included nonhumans.
Marx definitely means a qualitative distinction between humans and nonhumans when he says that there is a bright line separating “the worst of architects” from “the best of bees.” Nuts to that. If anything the distinction is only quantitative. And sometimes humans are worse than nonhumans on a quantitative reckoning.
Nonhumans are already on “this” side of social space. What does this tell us? Simple. Social space was never totally human.