It is you, OP, who is incorrect. Silver and Zone 1 get to board through the Sky Priority lane following the FC cabin and Diamonds/Plats/Golds. Zones 2-4 (or highest zone number) board through the general boarding lane. If you don't show up when you're supposed to that's your problem and you get to wait behind everyone else in the Sky Priority lane. Since you admitted you got testy and into a shouting match with the gate agent, perhaps you should go find the gate agent and apologize for being wrong and a moron. :/