I think that in a situation as proposed the LEO and I have similar expectations:
The LEO already thinks there is a problem, or he wouldn't have stopped me. He expects that I will not add to his danger by doing something threatening to him. I expect the officer to follow the law, safely for all concerned (whether I'm guilty of an offense or not).
Nothing requires me to give up my rights, including those requiring due process for a search, but all I have at the side of the road is verbal tools. If the officer decides to violate my rights, there isn't anything I can do about it there -- it will have to be in court later.
The LEO, however, has other immediate ways to defend his right to safety -- from a citation, to arrest, on up to use of his weapon.
It's not a situation of equal power. All I can do is calmly express myself, and anticipate that all will proceed as it should.