All public service agencies, especially L.E., have a lot of "dirty laundry". They would like to handle it internally (or not !). When it becomes public, it limits their options as to how to handle it. And obviously it makes those in charge look bad. So the less access those "nosy scannists" and media can hear the better for them.
It's true that SWAT operations, drug-busts, and undercover op's could be compromised if those well-known talk-groups are in the clear (as much as I like to listen in !), But DISPATCH, give me a break. They really need to hide Family Disputes, 211's, 459's, GTA's, 415's, etc, etc that happen constantly all day and night??? Yeah, I know the bad-guy could have an I-Phone, and find out the cops are on the way.. So what, they are usually GOA when the officers get there anyway. So just ban the broadcast of law-enforcement agencies on the internet. The legality of such is questionable anyway. I have no problem with that. The "bad-guys" are too ignorant to figure out how to program a scanner, but they can use an I-Phone or Droid.