It’s not all about humans. Our parks generally protect wildlife habitat. Whether you think that’s a good thing or not, I’m not going to argue about that with you.
It sounds like you think snowflakes like this “artist” have special rights that supercede both legal authority and moral consensus. I don’t, and I want this person out of our National Parks since the compulsion to share its “artwork” is too strong.
Do you really side with this person? Because your argument has changed from there’s no clear evidence of guilt to purposely man-made environmental damage is okay. I think most people will think you’re wrong in either argument.