Most of the people outraged on this (at least that I've seen) are people who make a profit off of the ad revenue gained from doing LP-styled videos on their channel. Looking at both sides, I actually sort of agree with the current actions being taken against these LP'ers. Keep in mind, that these aren't the typical copyright strikes people would occasionally complain about when Youtube received a vague notification of some kind of copyright notification on a video. This is just a simple block which only prevents the owner of the channel from receiving ad revenue from said video. Copyright strikes are typically more severe and result in the account losing certain privileges until the issue is resolved. So the people complaining are largely only angry because they're not making as much ad revenue.
Again, I'm not a strong supporter of copyright laws, but this is essentially people who were comfortable gaining a decent income from ad revenue getting pissed off that's been taken away from them. They're making money off of content they had no direct involvement in creating and expecting that the companies who owned said intellectual property to not catch on and stop it.
Then there comes the argument that their videos fall under Fair Use, which is pretty insulting to things that actually fall under Fair Use like reviews, journalism and criticism. I think if you look at the common LP'er, it'd be hard to argue that what they're doing is actually anything resembling journalism. It's just a bunch of popular Youtuber's getting pissed off they're losing out on a source of income, and are trying to appeal to the emotions of the average Youtuber by trying to pass it off as censorship or Youtube making another shitty mistake.