It sure is odd how these evil tools of the Man are never identified and flushed out by the noble, gentle, peaceful protesters before they start committing arson and shooting cops. Nobody noticed that these agents provocateurs were carrying guns? Nobody went up to them while they were getting ready to burn millions of dollars of equipment -- something which requires a lot more effort than just tossing a match -- and said "hey, don't do that, we're all about peace"? The pipeline protesters knew damn well they had bad apples, and they did nothing about it.
"Mom, he made me do it!" isn't going to save you in a court of law. Actual non-violent protesters, whom these people are not, would have taken someone advocating arson and murder and flung them out the door.