Protestors are annoying because they're omniscient. As soon as I would get a low animal welfare notification because of dehydration, I would send the animal straight to quarantine to get patched up. So theoretically the animal isn't visible to the public anymore AND is getting better, so nothing should happen. Yet not long after, suddenly protestors would show up to protest an animal that they shouldn't even know has low welfare -- and many times, the animal is already better by the time they make their way over to the habitat, yet they'd still stand there for a while shouting about an animal that is perfectly content.
I agree that you should actively be able to chase the protestors out of your park if you have enough security, but that could also come with a new game mechanic. If you chase them out early and you don't do anything about the animal's welfare, then:
1. Next time they come back, there's even more of them, which could cause an even higher penalty should the inspector see them.
2. They actually do damage when they come back, including potentially destroying barriers and setting animals free.
Anyway, I know this isn't necessarily a feedback thread, but I do agree you should be able to do SOMETHING about protestors, especially when they show up because they know things they really shouldn't/stay in your zoo long past when they should have already left.