Griefing, when done well, won't get you banned from anywhere, Fluttershy.
Sometimes, leaving while the admins are saying "hurr I'm banning you right now huehuehue" and joining with a different nick (even your current one backwards) and being more discrete and subtle about the griefing can get you out of trouble.
You can break all the stuff you want, afterwards, ofc.

destroying sections of the bridge isn't griefing

it would be griefing if i was knocking out the central pillars in an attempt to bring the whole thing down

trying to destroy blue's section as a green player isn't griefing. its playing the damn game. its no different than collapsing a fortress or a mountain - you are trying to deny the enemy of resources. in this case, it's an attempt to funnel them into the central corridor. its just too bad that certain people get rectum ravaged over a legit tactic

once the bridge goes down the bridgewars map loses a lot of its original game play styles and is a completely different game...

Pretty sure griefing is going to get you banned off of any server. its not just limited to bridgewars and it pisses off everyone.

the owner of the bridge wars server is a little bitch

sorry brah, but expecting the bridge to not be destroyed is a fools errand. its gonna get wrecked at one point or another. no need to ban peeps over playing the game correctly.