First, here's a quick take on it from an ACLU lawyer and yes, in Texas they can arrest you for failure to signal;
http://www.dailydot.com/politics/sandra-bland-arrest-video-legality/
Seriously? He asked her what was bothering her, and she answered. He could have just been done at that point.
She could have just shut the hell up and got her warning.
Less is more when dealing with the cops.
But no, for some bizarre reason he had to "order" her to put out her cigarette, which he has no power to do.
He sure as hell does!
Look Fly, I don't know where you're from but in the US when you're detained by the police it's a bad time to;
Sharpen your hunting knife
Clean your hand gun
Practice your Karate
Make sudden movements with your hands, feet ,body
He simply wants to hand her a clipboard so she can sign her WARNING that he's giving her, A lit cigarette can be used as a weapon and he simply wants her to extinguish the weapon before he continues with the encounter.
Much like "stop practicing your karate while I'm talking to you".
And she rightly called him on it.
No, she wrongly refused and got dragged out the car.
Much like if you don't want to stop practicing your karate you're going to get cuffed and shackled, put in a restraint chair, whatever it takes until you quit squirming around.
Had he just given her the warning and walked away, that would have been the end of it all.
She could have shut the hell up and taken the warning and that would have been the end of it all.