Chanting “Death to America” and assaulting Federal and other governmental buildings could easily be interpreted as insurrection or rebellion. Particularly if there was coordination and organization involved. I wouldn’t so quickly dismiss this out-of-hand.
No, it couldn’t. Let’s try to keep one foot in the real world. Being obnoxious and stupid in the way you exercise your freedom of speech is not insurrection. Nor is rioting or run of the mill civil disorder. No court would ever accept any attempt to label what is going on as rebellion as defined by the Insurrection Act. If California passes an ordinance of secession and orders the National Guard to seize Federal property then we can have this conversation. But given some of the discussions on FR relating to the events of the 1860s I would assume quite a few FReepers to loudly affirm the right of any state to withdraw from the Union.