nitrous oxide does not automatically induce engine damage. If that was the case, the company would go out of business. What kills engines is people who don't tune the engine after installing it. Nitrous is a lot like a turbocharger. You cannot just slap it on and go. You have to make adjustments before it's ready to run.

Furthermore, nitrous oxide is a drug. People get addicted to it and can't keep their fingers off the button. It wears the engine down much faster.