I understand they are deployed during emergency situations and are supposed to be the "internal" protectors of the United States on their soil. But, are they forced to do so and to openly deny their beliefs?

For example, if members of the National Guard sided more with the protestors and saw it as valid and more righteous comparitive to keeping and serving the peace in the U.S., do they just make a human decision to not follow their beliefs and choose to serve the U.S. instead or are they forced to?

I pose the question because I started thinking what if people in the police or the national guard simply started saying "Fuck the system" and chose to turn against the government in favor of the people. Scary thoughts because everything would change if these so-called authority figures joined the people. That would truly be a revolution.