When you read the discussion on the linked page you discover that the „partly false information“ involves the statement „America refused to apologise“. The Observador post points out George Bush was not president at the time he said he would never apologize, he was vice-president, running for president, and therefore his statement did not represent an official statement from the US, whereas Reagan, president at the time, did issue a statement of regret. Wikipedia has discussion of the fact Reagan’s statement was explicitly not a formal apology.
The Observador objection would seem like ludicrous quibbling and Facebook’s action absurd were it not for the reality that some significant segment of the US population sees Facebook as an arbiter of truth.