That is not a concern, though. Plex is a perfectly legal piece of software.
There are a bunch of reasons why it might be a concern, and only the least of them has to do with the legality of copyright use.
they assume Plex is itself a liability, which it isn’t.
Except plex has already proven themselves willing to ban users based on their use and streaming practices, so it clearly is a liability
It’s weird how corporate copyright assumptions have seeped to the mainstream and people assume that anything you do with your owned media is illegal unless you’re paying somebody.
If you live inside the US (or a state with trade agreements with the US) and are ripping physical media to store on your server and stream digitally, you are absolutely breaking the law. Doubly so if you are sharing that media with others outside your household.
'It's not a problem because I have nothing to hide' <- you are here.