While it is true that the total word count of the original U.S. Constitution is about 4,440 (compared to the Facebook policy’s over 5,000), these numbers do not count the subsequent Constitutional amendments, e.g. the Bill of Rights. If added, the word count f the Constitution raises to nearly 7,000. So already, this is a qualified comparison.
Compare that this to state constitutions. (Each state passes its own constitution that dictates the rights, rules, and framework of the state government for the operation of the state. e.g., California recently amended theirs to restrict marriage.) The average State constitution runs at over 23,000 words. Alabama’s has over 300,000 words! (Note, counter-point: a fact-filled discussion of state constitution length.)
As such, as the U.S. Constitution cannot be considered a long document apt for comparison, this is an intellectually dishonest claim, made without consideration of context, and made for sensationalism. A better comparison would have been the length of HIPAA policies, I think. Look, I only nitpick because we are motherfucking adults, capable of thought and reason, who should know better dammit. Be intellectually honest. Consider context. Qualify generously.