Many places have laws that personal use amounts of marijuana are not a crime, meanwhile selling tons of will put you in prison for life.
I think Facebook’s mechanisms are in the realm of 20th century propaganda efforts across a variety of countries (Americans/Soviets/Nazis). Is anyone forcing you to believe propaganda? Is anyone forcing you use Facebook? Is Facebook forcing you to be altered by their efforts?
Yet, we know how insidious propaganda was, and how coordinated and deliberate it was, and most importantly, how effective it was.
And honestly I think the legal argument is kind of moot. She is testifying in Congress, the body that creates the laws. If society doesn't like what Facebook is doing, we can create new laws that would give a legal basis to step in.