In what way could this possibly hurt NBC?In fact, it would have no effect at all. No one would ever notice.
Eastforker, you are correct. If NBC does something offensive, the effective response is to watch NBC only enough to see what companies are advertising there.
Then write those companies polite, but firm, letters. Tell them you will not buy their products as long as they advertise on NBC. Those letters will get their attention, and might make a difference.