"They weren't defending jack diddly squat."
Except you pointed out that they live in a "freaken mansion" which clearly indicates they had property they felt they were protecting.
Peaceful "save for the gate that was blocking the entrance to this so-called "
'private street'." Exactly, breaking and entering. The protesters were trespassing. The guns were meant to scare them off of private property.
If any shots had actually been fired you might (and I emphasize "might") have had a point.
Now, I personally would have just retreated to the house and let them pass. I do think they used poor judgement. But the property owners did nothing illegal. They just exercised their 2nd amendment right to bear arms. Charging them is clearly malicious prosecution for political reasons.