Right, and usually they would. Growth and retention is the lifeblood of everything Facebook does; Zuck would rather cut off his own right foot than intentionally lose users.

Which is why the only rational conclusion I can find with the evidence I see is that Zuck is either afraid that continued inaction was eventually going to land him in jail (or put him through years of Congressional investigations) or they have hard numbers showing that for every X people on the right they retain, they are losing N*X other users, N > 1.