ASTRO is kept afloat by bloated academic institutions providing generous CME stipends to their growing cadre of residents and attendings. They accept just about any abstract that gets submitted to inflate attendance and collect submission fees. It's legal money laundering. Donating to ASTRO PAC on the other hand requires the money to come directly out of our pockets. As unpalatable as ASTRO is as an organization, most of us are still ok with spending our use it or lose it "funny money" on the conference as an opportunity to catch up with old friends. Support for ASTRO PAC, however, requires real money. I think most of us find it challenging to part with our real money to support organizations that, as a result of their policies (or lack of policies), have left us with less real money to support them.
What I WOULD do, is sign a pledge of ongoing financial support contingent on the reduction of residency positions. If ASTRO PAC is so desperate for funding, then perhaps ASTRO should work to solve the problems that are the primary concerns of the vast majority of their constituents.