All they have to do is arm them with batons and pepper spray. Even paintball guns as they hurt like heck. At the same time, hire a local firm or even local deputies.
Environuts can be extremely dangerous as they have no rational governor on their actions. About 20 years ago there was an activist raid on a research center that was doing experiments on infectious disease. They released all the animals, some of which were infected with incredibly deadly disease vectors. Thankfully, the animals must have died before passing on anything contagious. But the possibilities are there.
Recent explosions at chemical plants may have been the result of unauthorized intruders stealing or simply causing trouble. (Some of the stuff at the plant that exploded in Texas can apparently be used to make drugs.)
Sounds like the usual suspects from Madison.