This is not a contradiction. Someone with privacy has the right to decide what they do and don't want to share publicly. Like you, I am concerned by how Facebook is used, and some of its societal implications, but this sort of extremist attitude helps nothing.
> Unfortunately for the average user (and even very advanced users) leaving Facebook altogether is the only option to maintaining secrecy of any kind. FB updates ToS far too often and nobody bothers to stay up to date with it.
This isn't true at all. While Facebook is somewhat sketchy about changing their privacy rules, if you don't want certain information made publicly available, you can just not put that information into Facebook (and yes, that includes Messenger). Any non-technical person can understand this.