Is there a name for this phenomenon? I've taken to calling it "the nihilist's excuse"

I call it race to the moral bottom.

Related: https://www.youtube.com/watch?v=KNqozQ8uaV8

I love it when I can guess what a video is before I click it. Exactly what I hoped it would be.

Similar to false dichotomy. "If we won't do it, <other evil guy> will".

I think it’s called being a “shithead”