I draw the line at illegality. Activists filming distasteful but legal processes are sketchy. Activists filming animal abuse in cases where the government turns a blind eye should be encouraged. Ideally the government would perform this function, but I don't see that happening.
That is what is wrong with this situation, someone with a camera chooses what to show or not show maybe there was an accident, maybe an inexperienced new employee or some technique that seems cruel but is necessary (de-horn, castrate, shear wool, horse shoes) but the film maker from a city finds disturbing.
For example near where I live there is a "slaughterhouse" that use the same techniques as other similar slaughterhouses but the one near me gets a lot of press and outrage.
The slaughterhouse I refer to is open to the outside it's on ice and it's seals not cow, bulls, pigs or chickens but it's the same process a bash on the head and then chop up the carcass. It just seems worse due to red blood on white ice and being out in the open not in a building.