The most chilling part is that even if they could swallow the cost, determining what a court would find infringing is hard. Of course they can filter out the obvious cases.
I have a two year old son. He loves Thomas The Tank Engine. And he loves Youtube and will frequently ask for "Thomas on the laptop". Most of the Thomas related videos on Youtube are actually re-enactments using the toy trains rather than copies of the TV show. There's apparently a whole community around this - with movies ranging from shaky clips of a kid playing to elaborate productions trying (though usually failing badly) to get close to the production values of the original series.
Some of them use snippets of the music from the TV show - how much is too much? Some use music I can't place - copyrighted or not? I can't tell. Some of them re-use dialogue. Some use text from the books. Others have invented their entirely own stories (but might still run afoul of copyright because they use the characters). Some has as their only similarly that they use the train sets as props.
The question is, how many of these would a court find infringing? (how many should they find infringing in a reasonable world?).
The end result is that to protect themselves legally, they'll need to reject everything that even has the appearance of being infringing.
This will likely throw out a massive amount of non-infringing content as well as a lot of stuff that is in a grey area legally but that the public will find ridiculous that they have to block. Vetting it will be far too hard
Of course, this latter part is perhaps the biggest light at the end of the tunnel: The chilling effect on speech are so strong and so far overreaching due to the lack of legal safeguards, that I can't imagine SCOTUS not throwing out substantial parts of this law.