Yeah, I think that's what bugged me (I looked for some photos, though admittedly I may not have seen all of them). I realize this wasn't a free-speech protest per-se, but a civil-disobedience one with an environmentalist goal. But even with purposeful civil disobedience, you have to commit some actual crime to get arrested, and it boggles my mind that
this can be a crime in the US. They were just sitting peacefully on the sidewalk, not even obstructing pedestrian traffic!
I guess I have a higher bar for what kind of disturbance is required to arrest someone in a free country--- violence, definitely; blocking traffic, ok; but sitting on a sidewalk with a sign, well, no.