I have absolutely not been willfully misreading. You can't argue that the guy saying he has a problem with Google's sign-in specifically has a point and also say that the data mining happening within Plex is WAY more intrusive. If the point is whether giving Google this data is a problem it must be worse than using any of the other sign-in options. But it isn't. Your data is as widely available one way or the other. It is reasonable to think Plex's visibility over your server is too much, I accept that, particularly if your use case runs afoul of their EULA...
...but then you can't tell me "I don't trust Google", unless your argument is you trust Plex more for some reason. Which you shouldn't. It just doesn't follow.
Oh, and they do sell your data for advertising. There's an opt-in for it, though. Since we're talking about legality, it'd be a punishable offense for them to sell your data without your consent, which is why that's there, and they do need to tell you what data they collect if you request it.
And no, I am not liable under US law. There is a treaty that requires both parties to meet those requirements, but US law isn't directly applicable over here. What is applicable is our own legislation made to comply with those trade agreements. Which includes exemptions for private copy.
As far as I and every piece of legal advice I've seen about this knows, anyway. If you have a source for how apparently US law is directly applicable to any country they have a trade agreement with feel free to point me to this insane new paradigm of international law, though.