Here is the issue: it is more than mere competition. We co-exist in a delicate balance with the rest of life, or at least we used to. Now we threaten to destroy them, and the planet on which we depend, exactly because of this implicit belief that we compete with them instead of relying on them.

Why does preservation of human civilization depend on exterminating wild nature?

The reason to persevere organic forms around us (plants, animals, fungi, bacteria, etc.) is rational self-interest.

Bacteria are necessary for our bodies' healthy operation. Organics generate the oxygen we need to breathe.