why is burning bridge so bad? there are other ways to cross river than a bridge

Now that I've officially been sacked, I keep being told not to burn any bridges. Of course the sensible part of me knows that I should do as suggested and not haul off on the boss and the people that have made me so miserable for the past two years, but the other part of me really really wants to. And I mean really. In my family if you have a problem with someone you let them know. I cannot even count how many times my brother and I swore at each other and spent hours yelling about exactly how much we hate one another. Now adays my brother and I have really open and honest relationship where we can still yell and swear at each other but we always make up and appreciate being able to wig out on each other. It's so relieving to tell people what you really think, especially if you can use one of George Carlin's 7 words to never say on tv in the process. So if your work is supposed to be a kind of family, why can't you rip into them the same way? Because work is not a family, instead it is a group of people largely pretending to like one another but secretly not giving a rats ass if one of them got hit by a bus on the way to work. True, there is usually one or two people that you become friends with, but the rest of them...feed them to the wolves! Realizing the wisdom in that trite saying however, I have bitten my tongue until it bleeds and instead dream about telling off my boss (really, I've probably had at least 4 dreams where I really tear into him). And because I realize that while yes, there are other ways to cross a river, like making a home catapult, that is much more difficult than using the damn bridge, and so instead I will choose to seek my catharsis through some time honored passive aggressive behavior. I plan to make as big a production as possible when I pack up my stuff this Friday and may even hide something really smelly like a rotten potato or leave a honey trail for ants in my office. And of course I'll finish it with a great big "I know you are but what am I?" while sticking out my tongue as I walk out the door.