that's true of course. but i'm afraid that the revelations of the past months have almost turned "jumping to conclusions" into a legitimate response to this kind of information.
I guess they'd still be hoovering up everything they could, just in case, if it weren't for the threat of terrorism. Public opinion is strategically important (if a foreign power starts a war, how will their people react?), but it wouldn't be so important.
Next on the NSA revelations list: A backdoor software "implant" capable of exploiting holes in everything from Froyo to KitKat, and which subverts the device's power management circuitry, such that a remote command can short-circuit and overheat the battery. Results, and especially the likelihood of explosion, depend strongly on battery capacity and charge state, but in-house testing suggests probability of fire should be ca. 95%+ across all device models susceptible to the implant.
(Speaking of which: "Implant", I like that choice of term, it's got just the cyberpunk flavor today's world needs.)
i'm guessing most people thought that spying of US agencies was an activity that was carried out abroad, and aimed at real threats.