The headline refers to FBI's aggressive questioning of environmental activists to make sure they were "playing nice".
The FBI has labeled ecoterrorism as the top domestic terror threat since at least 2005. That puts “highly destructive ecoterrorists” above “hate-filled white supremacists,” “violence-prone anti-government extremists,” and “radical separatist groups” — descriptions from a 2009 FBI press release on the agency’s website.The political operatives of US capitalists are indoctrinating their enforcers to believe that environmentalists are mostly "terrorists"--today's version of the old bogyman, "commies". Clearly, as many people realize that there are severe threats to the environment by the increasing use of fossil fuels and other hazardous practices, they are becoming activists who protest against these activities. However, since capitalism cannot survive without growth from the use of relatively cheap fossil fuels, such activists are a real threat to the system. Hence, the aggressive use of FBI agents to intimidate protestors.