i think everyone here has great advice.
i have always been very outspoken at my jobs, and really spoke out in a big way when i left the job. my feeling is if the bridge is unsteady, BURN IT TO THE GROUND.
but i have been fired a lot, and made enemies that way. it works for me, it is the right thing for me. because i feel like it is the real and true me to speak out about crappy jobs and burn bridges in a firestorm if i need to. but it definitely closes doors and hurts feelings.
i would say tact and quiet grace is the smart and best and RIGHT way to go. don't burn bridges.