I am not a fan of gun battles like the recent biker shootout in Waco, but they may be an inevitable, and possibly legal occurrence in a 'stand your ground' state. The first biker to threaten another biker or his property with harm, if found, may have broken the law.
After that initial disturbance, a chain of 'stand your ground' actions, self-defense actions seem to have occurred. It is legal under Texas law, see below, to use lethal force to protect yourself, other threatened persons, or property. There is no requirement in the law to back down or retreat, anywhere, even a public place.