Nothing wrong with blocking comments at all. In all seriousness, it is incredibily rare that you ever find a youtube comment that is actually of substance. So really there is very little lost.
I have a pretty big blacklist of words that will stop comments being shown before I approve them too, I can take criticism but I don't tolerate just bashing my content and I don't want my viewers to see it either.
PewDiePie did it to stop self-advertising and people trying to leech off of his success, that is really the only reason he did it. Many people don't like how G+ works because people with more subs get higher places in the comments section regardless of their comment because G+ assumes people want to read that persons comment more than the average person.
It's not being thin skinned, it's about having a bit of control and keeping a bit of order in your channel.