I think I understand what you mean: a critic generally wants to have his or her point of view understood and acted upon, to which you could conclude that they might ultimately want to be able to be silent.
EDIT: maybe I didn't understand what you mean ;)
However, I'd argue that a single act is really just a grand gesture. To expect to silence critics with such a gesture is unrealistic - and doesn't do anything to positively resolve the issues involved with any cause worth fighting for.
The privacy issues that Facebook might need to address are deep and wide ranging. Facebook instigates cultural change - it's the nature of that change which should be up for debate.
Okay, to a degree I'm playing semantics .. but silencing an opinion isn't the same as reaching a resolution. To 'quell' suggests a pointed action, which puts the purpose of quietening the critic's voice, above resolving the critic's concern.
A disingenuous response is usually designed as a full stop, rather than way to carry on a conversation.
If they're truly into the idea of promoting user-ownership of data, there will be more done to allow it (i.e. this will be first step).