Facebook listens to your phone's microphone

<Facebook says explicitly on its help pages that it doesn’t record conversations, but that it does use the audio to identify what is happening around the phone.>

Well, that's comforting.

<Turning off the microphone in a phone’s settings is relatively easy>

Really? Turning off the mic for Facebook (or even globally to apps) without making it useless is "relatively easy?" Somebody, please point out to me this feature on Android.