It is a matter of definitions, and it's a matter of avoiding a fallacy. Just because "we come from nature", doesn't mean we're bound to whatever patterns of behavior we observe in animals, and it especially doesn't mean the "nature" tells us what we should or shouldn't do. The world of non-human living things is a very bad place to look for lessons in morality.

"Humans are different" isn't arrogance, it's observable reality. And we need some words to separate the categories of "things done / caused by humans" vs "things done / caused by everything else" - hence the common meaning of "natural" and "nature".

> the building blocks of a human are the same as everything else in the universe (as far as we know).

Building blocks of everything in the universe are the same, but there's still meaningful difference between things.