I think cops have a responsibility to be reasonable, especially when we are talking about nothing but a failure to signal. I disagree with this all-powerful cop position where the person must cower in submission. She was responding to his jerkiness.
And escalated the situation.
There are bad cops just like there are bad service station attendants.
You will never win when they have pulled you over.
Do what he says, sue him the next day.
Really, you want to just sign that ticket and drive off. Endure him for those minutes then sue him.