Texas law allows the use of force and deadly force in the defense of a third person, if "the actor reasonably believes that his intervention is immediately necessary to protect the third person."

This guy definetly needed some immediate protection. I don't know if I would wait til after I have confronted the big guy to pull my weapon. Pretty tight quaters in there to draw on somebody who is watching you. Wouldn't you be justified in pulling your weapon under
PC s9.04. THREATS AS JUSTIFIABLE FORCE. The threat of force
is justiied when the use of force is justified by this chapter. For purposes
of this section, a threat to cause death or serious bodily injury by
the production of a weapon or otherwise, as long as the actor's purpose
is limited to creating an apprehension that he will use deadly
force if necessary, does not constitute the use of deadly force.
Also the one where the big guy beat the man sensless was in a pizza parlor full of people waiting for their food.