I remember reading in the papers a while back that ALF, PETA and such like had been/trying to sabotage the badger trials by reintroducing badgers to culled areas. But its probably just a Daily Mail conspiracy...
As far as i know deer aren't protected, unlike badgers, so if the herdsman/gamekeeper suspects that a few are carrying, he can have them culled legally and discreetly.
The public is ignorant about how much of a danger bTB is to cattle farming. They just don't like the animal rights people putting culled badger pictures everywhere. Its the same as in Darfur, people see on the telly people being raped and killed by the janjaweed, they don't like it, but at the same time they won't do anything about it, it'll inconvenience them.