Free speech is not only about articulation. It's also about the ability to share, disseminate, and influence others.
Freedom of information flow isn't the same thing. Democracy works best with an informed electorate. Information flow without discourse is just indoctrination. And that's what Facebook (unintendedly) optimizes for.
Depending on your definition of "thought".
That's a rather strong opening to limiting free speech. Who gets to decide that my speech was without thought? Is there an approval process? Can I repeal the decision? Do I have to document my thoughts before I speak to prove later that I did indeed think before I spoke out against the people that make those distinctions?