Seems like they do some times. Savage will be gone in 3 weeks and they will pay off the balance of his contract if its true that all national advertisers have bailed out on him.
I think there is a major difference between a handful of Freepers sending a terse email to a company threatening to personally boycott a product and a national organization's similar efforts. Your email will likely be read and promptly deleted by some low level staffer. GLAAD and the NAACP exist for this kind of crap, they have plenty of pony-tailed sniveling lawyers who get paid to do this all day long. They know what buttons to push with the advertisers to get the right response - lawsuit threats, threats of national ad campaigns against them, working deals with competitors for all GLAAD/NAACP members.
MSNBC, FOX, CNN are in business to create programs that bring a large audience to a group of advertisers. When either group doesn't show up the show is over.