You two are talking past each other. Yes, the NSA is a foreign intelligence agency. But then why is it spying on citizens? Ostensibly to prevent bad things from happening. Yet bad things are happening, that could presumably be stopped with information gained from said spying. But no one is using the information that way. So why should we let them continue spying?
I think there's another sliver to be added, though, because the NSA can still give the excuse that the answer to
> why is it spying on citizens
...is that it's doing that to prevent foreign attacks, not eg. mass shootings.
Furthermore, even if it were doing anything useful with its domestic spying, such as preventing domestic crime, obviously we'd all rather address plain ole' shootings, which take many more lives than mass shootings.
I think that sums it up.