I use the line "I will not resist your illegal searches and/or seizures, but I certainly do not consent." They usually try to re-iterate with different phrasing that is more aggressive, and I simply refuse to repeat myself. They try to get you to change your words to theirs, and choose words that would imply imminent violence. It is drilled-in FDLE training, I'm not sure they even realize they're doing it much of the time. Always rephrase in a problematic way, and try to get the perp to agree with your wording. Those are the only words that will then show up in the report. Don't EVER agree to their rephrasing. "Sir, that is not what I said." Expect to have a hard time with the ones who pull this, they really don't like it when you are clearly hip to their mind game and too sharp to fall for it.
"I'm trying to respect you, I ask that you respect me." Is a line I also use to make it clear I'm not just being a hardass that wants to mess with them. I really don't want to mess with them. But so few are willing to act civilized and respect me, that I end up having to go hardass anyway.
The first few times it can be scary. But you get used to it. My pulse still races, but I can hold my line and not waver or let it show now. I know only too well that they can still arrest me for no damn reason at all, make up false charges, fix it in the report, etc. Being Right and having Rights doesn't actually protect you from the damage they can do by abusing their position. I try to show them the same basic respect I would show for any other human being and simply state that I expect the same. They refuse, I whip out the 'Why am I being detained? I have nothing further to say." Conversation over.
The real assh0les get the "You've made it very clear that I am not free to go, I have nothing to say to you."
Let me be less subtle: DO NOT ASK IF YOU ARE FREE TO GO. Does a rape victim ask if they are being raped? What answer do you think you're going to get, if you get one at all? Make a STATEMENT that you ALREADY FEEL THAT YOU ARE NOT FREE TO GO. He will then have to acknowledge detainment, or deny that was his intent to detain you. If you ASK, you'll get no answer, no straight answer, lies, etc... YOU are the one who decides if you are being detained or not. If you are not free to go, YOU ARE BEING DETAINED. Don't ask. It's stupid and you'll just go in circles. Ask WHY you are being detained, or state that you know you are being detained. There is no QUESTION of the detainment, don't make it into a questionable thing and ruin your own position. If the civility has already degraded to the point where you've reached this impasse, manners and respect are already out the window and the Cop is the one who disposed of them by pushing you to assert your Rights instead of Respecting them like he should have.