Considering humans the most competitive species is also something that could be called into question. We certainly think we're special, but we're probably falling into Dunning-Kruger territory.

I think the only obvious route is to treat other living things the way we would like to be treated - after all, we have a common ancestry and a case could be made that we're just one big multicellular organism

I do buy the golden rule as the only unarguably reasonable philosophical principle (I hold it pretty highly as an essential combination of rationality and empathy), I'm just arguing for the sake of it.

The reason I consider humans the most competitive is because we could potentially wipe out any form of life (for some, we would have to go too). As for the special thing, I don't think we're special in the sense that we have some innate quality that separates us from other animals, we're just more intelligent. Some unknown gap between the smartest animals and us results in the situation we see today: humans have created technology and industry, pursued math and science. No other species has, as far as I know (or at least not to a degree that makes it significant relative to human understanding)

This is all hyperbole. From the egoistic perspective, live is just a figment of imagination, there is no other, just ego. This might sound like a matter of semantics, but it reminds me of this: Virtue is mainly a question of how to treat oneself.