re: Cop stands up to gun nut in Texas.

As a cop, I have the right to approach anyone on the street to talk with them. That is a consensual encounter. The moment I use my position to prevent the other person from leaving (a reasonable person would feel he/she is not free to go) the encounter has risen to some form of detention. The question is whether the detention is legal or constitutionally defensible.

This type encounter - exercising a legal activity that concerns other citizens, thus getting law enforcement involved - is only going to get resolved at the USSC level.