Hmmm, I dunno.
The thing he seems to be overlooking is the part that IS positive. It doesnt have to be glowing comments. It's the fact that such an enormous amount of people continue to subscribe to him, continue to watch all of his videos, and stuff like that. That IS the "positive comments". And in his case it's not just positive, it's absurdly positive. But as in many cases, because it's not in the form of lots of words, it doesnt get thought about.
Not to mention the negative bits.... there's a line I've always liked, which is "The negative ones are always the most vocal". When people are angry or see the need to vent, they become louder, they put WAY more effort into getting themselves heard. As someone with a fuse so short that it might not exist, I understand that part very well. Wheras the positive ones? They see the negativity and think "Ugh. This comments section is made of jerks. I'm just gonna ignore it, I dont need to post anything to enjoy the video". Alot of times, people dont seem to think about that one either.
Hell, even I do that one. I tend to hang around forums related to things I like, but there's one major exception, which is the Minecraft forums. I love that game, and enjoy discussing it, but those forums.... there's 10 gazillion people that really love that game, but those forums would have you believe the exact opposite. They're a hideous, festering pit of sorrow and tragedy. So I avoid them like the plague. The negative players are so ridiculously loud that the positive ones just dont want to bother anymore. They just go and enjoy the game, while the negative ones continue to whine.
I know stuff like this is difficult to deal with, but.... one way or another, his current feelings about it are in a large way due to his own perceptions of it and his responses based on those perceptions. If he wants to keep it up, he's going to have to make a change to that one way or another. And really, the guy really DOES have TONS of positive pointing his way.... if only he could see it.