Boycott the RIAA and MPAA? Hypothetically, that's a good idea but it will fail in practice. Boycotting the RIAA means never again purchasing music from a major label, setting foot in most major movie theatres, or purchasing/renting most DVDs. That limits most people to independent music labels, theatres, and movies. While one could argue (and, to an extent, I would agree) that there is plenty of good independent films out there, you're not going to see a Spiderman, Superman Returns, or other similar special effects/blockbuster films. This, to me, is a terrible loss.
No, the problem is not that the RIAA and MPAA constituents are allowed market their product but instead that the RIAA and MPAA have a strangehold, once could even say monopoly, on political influence regarding their products. Here, in the States, I don't believe that our Sherman anti-trust act has anything to do with political influence but instead is leveled against market monopolies. Of course, it's highly unlikely, in this day and age, that politicians would ever admit the degree that these lobbies influence their decisions and consequently pass a law to further reign them in. That would be result in the campagin finance reform that we've needed in the States for years and may never see.