I like pinning shit like that on the FBI. It's something that they're perfectly capable of doing, even if it should turn out that they're not implicated in this particular offence, it's something they've done in the past (not vandalizing graves, necessarily, but other outrageous, provocative acts designed to turn the general public against the peace movement) and folks need to be reminded, and they can't be reminded too often, what duplicitous scum they can be. (In the Sixties, they tried to blackmail Martin Luther King into committing suicide.)
It's also good to remind folks not to rush to judgment when they're told to blame the Left for any particular outrageous act. Things aren't always what they appear to be on the surface, agents provocateurs abound, and basically you should always keep in mind that it's the Left who are the good guys, they're the only ones who are acting out and speaking out against war, against torture, against indiscriminate killing and raping of civilians, they're the ones who want a better world for everyone.