He didn't fight them because it was cut and dry. It has nothing to do with big corpo, it has everything to do with IH thinking he could get away with copying an article without giving credit for it. If you lie and you know you've lied and then someone else figures out you've lied and they have clear undeniable proof of it, the only fathomable reason you would fight back is if you're retarded or you have an inflated ego.
Frankly, I'm starting to think IH is retarded because giving credit to someone else seems like it should have been the easiest and simplest thing to do. This just begs the question how many other content cows are filling up their troves with uncredited plagiarized material just to make ends meet and satisfy YouTube's hideous algorithm. And nobody is the wiser because, like KiwiFarms, people on social are becoming less and less objective and more and more reactionary.