The "evil bad guys" are a subset of the "general public", so the collection of information on "the evil bad guys" necessitates the collection of information on the general public.
It's all just a matter of definition. "We have to collect data from Everyone because the bad guys are a part of Everyone." It's simple logistics, we can't just collect the data from the bad guys if we don't know who the bad guys are, and even when we do, the bad guys pretend to be part of the General Public and so we need to spy on the General Public in order to catch the bad guys.
Look, it's all really complicated and we can't expect just anyone to understand our motivations. We're really only looking for "the bad guys," we promise. We totally ignore all the rest of the data we get from the "good guys" and we certainly don't build dossiers in the event that "good guys" suddenly become "bad guys".
Listen, just chill the fuck out about all our surveillance, we're totally not looking at you, unless we are, in which case you deserve to be spied upon because we said you're bad. And our accusation of your badness will require a secret court to clear your name, but you can't know what that secret court has determined because it's secret and your a goddamned terrorist if you think otherwise.