Because, for example, few Americans consider Germany to be an "enemy" or even an "adversary", yet:

https://www.theguardian.com/us-news/2015/jul/08/nsa-tapped-g...

Nobody in the IC believes allies aren't constantly spying on each other. Germany and France are notorious for doing it to support their state industries. Like it or not, in the intelligence arena, the US and Germany are rivals.

Because the NSA breaks into US-based companies too.

I'm sure that's happened, but there's a reason the EQ dump included lots of vulnerabilities for Chinese products nobody in the US deploys.

"Enemy" is a weird word ("adversary" is probably better), but however you slice it: NSA's mission includes real ones.

That is entirely irrelevant to people who are still getting hacked because of these hoarded vulnerabilities.

I don't follow. Could you make this argument more specific? Who's doing this attacking? What kinds of vulnerabilities?

Stated as vaguely as you have, that's a hard argument to rebut. I tend to agree: the world would be a safer place if everything was publicly disclosed immediately. But even NSA's opponents tend not to support that as a policy objective.

Their tasking, though, is to break into foreign ones. They see breaking into domestic ones as necessary to do that (and I can see why they might feel that way, even if I don't like the result), but I don't believe it's part of their core mandate.