Because I'm a Buddhist and a socialist, many people assume I'm a humanist, as they think Buddhism and socialism are both humanist. I think the opposite. The Buddhist understanding of interdependence precludes the arrogant view I call "human exceptionalism." And if socialism is only for humans then it's not socialism, because it's still class-based, with bosses and bossed, exploiters and exploited.
Although I have criticisms of the book, I like the subtitle of Timothy Morton's Humankind: Solidarity With Non-Human People. We need to see not just all clearly-sentient beings as people, but also rocks, walls, pens, machines, as people.