The scope of these activities, especially when combined with the NSA's (and GCHQ's) indiscriminate "hack everything" attitude. When the NSA attacks so much infrastructure - including standards they are supposed to be supporting - at some point they start creating a reasonable doubt about the true actors behind any network attack.

This could have various consequences, but one obvious one is how it affects a jury. It would probably be a lot easier to conclude there is a reasonable doubt the accused did not commit some type of computer or network crime when the NSA is attacking so much infrastructure. If the NSA was known to be targeting legitimate targets with limited, targeted activities that did not affect everybody else, the doubt that any random computer crime could have been the NSA's responsibility would not be reasonable.