We're as boggled about all this as you are, obviously. Ruffalo has been organizing screenings of the new documentary
GasTown GasLand, which follows the journey of a man (not Ruffalo) as he visits towns and individual homes affected by the drilling of natural gas companies. It's a bit Michael Moore-ish, yes, but the preview clipwatch that heredoesn't allude to any terrorist-type activities.
Perhaps Ruffalo has been doing something a little more than just organizing the screenings, we don't know, but he's hardly the type of person we'd expect to land on a TSA Watch list. So much for celebrities getting the star treatment even at airport security...