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"the LEO is suppose to do what"
The LEO is supposed to be a professional.
They are supposed to be a reasoning, thinking, adult.
They should be above trying to harm someone, be it legally, physically, or monetarily, just because the person annoyed them.
They should abide by their mission.
I think that they should do their duty.
So what exactly do you believe their duty is? To enforce the letter of the law, ie. speeding ticket for going 56 in a 55, or to enforce the intent of the law with discretion allowed for minor technicalities?
If the officers mindset is, I'm going to just give them a warning for this violation as long as things go well and there are no red flags, how is that different than saying, if you're an a$$, I won't let you off, or I'll make you pay (what you owe)?
To me, it's a matter of perspective. If there was a valid reason to pull you over, then there's a valid reason to issue a citation. Being nice might invoke officer discretion and get you out of that.
Of course if you are dealing with a bad apple and just got pulled over for driving while black or something similar, then it really doesn't matter how you act. They're looking for an excuse.