Terrorist Speech: Parental Pushback on Critical Race Theory Spurs FBI Domestic Terror Probe

Attorney General Merrick Garland orders the FBI to launch a domestic terrorism probe in the wake of a series of parental protests at school board meetings over critical race theory curriculum in public schools. Garland got goaded into this by a National School Boards Association request to the Biden administration. What's the true threat here?
----------------------------------------------------------

First Amendment
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

I notice in this list of Rights that it does not differentiate between Federal, state, county, city, town governments. My question is: How does AG Garland find the RIGHT to declare possible domestic terrorism for the RIGHT to petition the Government for a redress of grievances?