my guess is that they hoped to pull themselves up as they pulled google down. they probably feel like they are doing nothing wrong, and that it's unfair that they are criticised more than google. so they want to "level the playing field".
i don't think they thought it through in absolute terms, just as "getting even".
but if you want a pro-fb response, i'd suggest going to quora and asking there (or just searching - there's probably already a discussion). they have a couple of ex-fb people who will provide some "balance" (in particular, look for yishan wong).