Right. Piss off a cop. Brilliant! The balanced and calculated reactions of these individuals was very impressive, I only wish I had their fortitude and thoughtfulness in such situations.
"Sorry, officer, I don't understand your question."
"Are you paying to be a passenger in this vehicle?"
"I'm sorry, officer, I want to help you, but I just don't understand how this involves me. I'm just a passenger here."
Most cops will just give up asking the question there. If the officer pushes the issue, he's being an asshole, but you can still very politely invoke your fifth amendment rights: "Sorry, officer, I should have an attorney present to help me with these questions."
At that point, answers to any further questions (if any: standard police policy everywhere is to cease questioning immediately) are completely inadmissable (Edwards v. Arizona, 1981).
You can beat the rap, but you can't beat the ride: that's true. With that said, the cops who will bring you downtown for asserting your rights are exactly the cops that you really shouldn't be talking to.
(IANAL, FWIW; I'm just an occasionally rude anti-authoritarian citizen who has to mentally practice polite assertion of my rights so I don't accidentally piss off cops who, in their view, are just doing their jobs.)
You're not dodging the question, but offering a well-understood reason, and the reason involves something real but external to both yourself and the LEO.
The right way to handle a police stop (in the US): https://www.youtube.com/watch?v=eDJrQBwJpqk
Starts at 1:10
They are asking questions in a leading way, its how they are trained. You just have to be diplomatic and nice about it.
I have been stopped before and asked how fast I was driving. I simply said I was not sure but I thought it was at the speed limit. Unless the police have evidence they can only have a talk with you.