although i do not have any direct experience or knowledge with this, i have heard the Travis Co. District Attorney's office vigorously prosecutes gun related charges.
that being said, if this incident were to happen in this jurisdiction, i am not certain which way it would play out.
i would say that someone choking someone else is a use of deadly force and if that were the case, then the use of a firearm would be justifiable.
however, it appears that this was an ongoing feud between the two. also, if they were arguing about which car salesman gets the next "up," [car salesman jargon for walk-in customer] then the argument really should not have escalated to physical force.
however, having worked on a car lot, i have seen unscrupulous salesmen scoop the next "up" from the next guy in line. kind of like a taxi driver cutting in front of every other driver in line at a taxi queue to scoop up the next customer. i wouldn't exactly resort to violence, but i don't think it is improper for the salesman who was wronged to at least verbally express his discontent to the vulture salesman.