If you look at the ThinkProgress org site, it's littered with anti-pipeline crazies. They also have an article on the Pittsburgh Mueller "Instant semi-spontaneous riots" (just add Soros $$$). I'd guess most lefty sites too. Just happened across TP (apt initials) lookin for more on the Mueller charade.
I'd bet a fin that it's lefties of some sort behind the explosives heist. Surprised the ATF reward is only $10K. Usually they try to make a major example of thieves who steal that sort of stuff.
Could also be the RoP, but I'm bettin pipeline loonies.
Maybe they'll kaboom themselves.