The warning is actually about substance abuse or mental health.
Seems legit in this case.
Sure, but it's interesting that Facebook will do this to someone at the behest of a 'friend'. It makes me what their limits are. Believing this conspiracy theory is crazy, but so is believing in an invisible sky-daddy who tortured his son to forgive you for your sins.
don't they have freedom of speech there in the US?
Only applies to governmental restrictions on speech. Private organizations, like Facebook, are largely free to impose whatever restrictions they like.