Some people need to inflate their ego
After reading this article my first reaction was simple: "Meh, one youtuber mocking and making fun of another. Of course that's going to piss some people off...". Then I actually watched the re-uploaded video and... As said: some people really should put some work into keeping their ego in check I think.
I mean.. they weren't negative, they weren't mocking the guy or his video or anything, but merely commented. It's the golden rule of the Internet: if you don't like people commenting on the stuff you do or share then maybe not comment and share in the first place.