This exploit is something that needs to be specifically installed by someone - it's not something you'd use to exploit the masses, it's something you'd use to monitor a target further once you already had (perhaps temporary) root access.

In that sense, it's basically just bread-and-butter spy work. It's hard to accept that the government has any reason to monitor the population to the extent that the NSA does - but it would be conversely completely foolish to say that they have no business developing attacks for computers - it would be like saying they have no business developing lock pick tools or electronic bugs.

History has shown that a strong nation has at least some need for intelligence and counter-intelligence, and the US has historically had incredibly poor capabilities for both, which has lead to the deaths of thousands (thinking about Vietnam intelligence specifically).

It thus seems at least foolish to criticise what's clearly an impressive targeted exploit - which to some extent demonstrates the US' dominance in the field.

This isn't something that the public has any business knowing - this is just plain espionage.