Ascribing free will to humans is to open a Pandora's box of pandering, retribution and blaming of victims for their unfortunate circumstances. Blaming the victim is a favorite pander of conservative politicians. "The unemployed are lazy." Did 13 million people suddenly become lazy slackers at the onset of the Great Recession? Isn't it more likely that the unemployed are mostly ordinary people who got caught out by an economic slowdown not of their making? Seeking to stigmatize and humiliate these victims by requiring them to submit to drug tests, derives from inappropriate assignment of their state to acts of free will.
Policy after policy introduced to punish victims of circumstance derive from illogical application of the false notion of free will. While many liberals no doubt believe in free will, it is the conservative Republican Party and the Religious Right that have based their entire political and religious dogma on blaming the less fortunate for their circumstances. Want to collect unemployment? Take a drug test. Good grief! Haven't these people suffered enough anguish and humiliation without new government regulations adding insult to injury?
Discarding free will is of course not the only route to a more liberal political outlook, but it is surely based more firmly in fact-based logical reasoning and best science than the alternatives.