A possible line of thought in response...

Nature made us self-harming, as well as a number of other characteristics or behaviors some of us see as bad.

Each person can make choices about going or not going down this path.

As social animals we can create cultures to discourage self-harm. Of course, such measures will be opposed by others, including those who profit from others self-harming.

At the highest level, we have many impulses, whether unique or not. Every species has genetic programming that each member obeys at times if not constantly. In the big picture, self-harm is not really something to judge.

What we have (is it unique?) is the ability to choose, and to choose through reasoning.