i'd honestly agree with you 100% if he weren't so injury prone. but i think there's a good chance he's back on the DL before the seaosn ends--and then you're not getting the package they got from the cubs from any team. his numbers over the past month are off the charts and he's healthy, so you can either trade him now while he's at his peak, or you can gun for the playoffs, exercise the option on him, and then run the risk of him getting hurt again. 7 mil down the drain is nothing to the red sox, but it's a lot to the a's.
as far as the team goes, i dont think they make the playoffs anyway, but if they hold onto harden and he gets hurt in august and misses the rest of the season you figure they are done. if it happens to him in chicago an the a's miss the playoffs at least they have what they have instead of a dude coming off an injury who you'll have to begrudgingly exercise an option on just so you can hope he stays healthy and is pitching well next year so you can trade for him for a lesser package since he'll just be a half season rental at that point. plus, gallagher is a good talent and if dudes like gaudin, smith, and eveland can succeed in oakland i'd bet a paycheck that gallagher can too.
i dont know if the fans will be that pissed off anyway. im familiar with their philosophy, you're familiar with their philosophy, so im sure they are even more so than us. billy doens't like investing long-term in pitchers, there's always been a ton of turnover in that rotation. they draft mulder, trade him to stl for haren (among others), keep him for a few years, trade him to ari for smith and eveland (among others), and eventually smith and eveland will be traded for other good young pitchers. if im an a's fan, i notice this and put my trust in billy