The subset of doctors who expend probably significant time/effort getting on the governing board (or whatever it may be called) of the AMA, maybe have different opinions than doctors in general? (I've found this sometimes to be true of professional organizations/unions)
True, this is indeed possible. However, note that the FDA survey cited only asked 500 physicians. The survey was also done in 2004, which I believe is prior to the cracking down on gift giving and pharmaceutical companies giving kickbacks to physicians. If I remember correctly, DTC advertising spiked after this happened.