The mitigating factor is that she was arrestable for an offense, at least in Texas (driving with a suspended license.) Once an actor is under arrest, there are grey areas of conduct by the officer, depending on all factors perceived by an officer. I'm not saying that this wasn't a serious abuse of authority, but even as a civilian, this wouldn't have been a felony offense. Let's not make it worse than it appeared; it was indeed alarming and humiliating, but the woman wasn't harmed.
The ‘driving with a suspended license’ chrage, later dismissed perhaps because of a clerical error?, was discovered after the assault! There is no excuse these cop thugs should not have been fired and brought up on criminal charges!
The problem is, talking on a cellphone, and most other minor traffic violations, aren’t arrestable offenses. You can detain a citizen to give them a citation for something like that, but it doesn’t merit an arrest.
However, if an officer approaches the traffic stop in a confrontational way, hands on weapon, and barking orders, the citizen might fail to comply with something quick enough, or to the satisfaction of the officer. Then, they can claim “resisting arrest” or some such charge, and have much more leeway to deal with their suspect.
Now, how someone can be resisting arrest for a non-arrestable offense is a matter that might fascinate a Zen Buddhist, but doesn’t seem to phase our judicial system.
In any jurisdiction in the western world a man who attacked and hogtied a woman has already harmed her and has committed the felony of assault. You might find some shred of cover to excuse or mitigate this behavior but these cops should be behind bars.