Meh, you don't fight the police when they've stopped you. You just don't.*
You put on your serious-and-concerned face, you say "Yes officer" and little else, and you cooperate.** Then (if appropriate) you fight them like hell in court.
On the street it's your word versus his, and the deck is stacked high against you. In court, you're on a much more even footing.
There's a time and a place for everything.
* Unless you believe your life is in immediate danger, but that's whole other topic, and kinda tricky to deal with correctly.
** With the exception of searches. You never agree to a search of anything. They may do it anyway, but you state clearly, "I do not consent to you searching my person/car/boat/home/whatever." It matters that you say this.
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