You're missing the point. Even when the spying is used in "bad" ways, it's better for the spying to be accurate. For example, rather than randomly throwing students in jail for searching for the wrong library books, they'd only be jailing real dissidents. Of course it's wrong to do either, but if they're going to do it, everyone is better off if they do it right.
Objectively define "real dissidents" with a definition that can never inaccurate, as well as impossible to abuse by any and all that have power within such system.
Terrorism is a low risk in the US, these programs seem to add little to just having investigators follow leads and intentionally infiltrate groups or paying informants or similar, and the US government has a long record of targeting groups that the powerful don't like.