Regardless of the laws here I'm gonna sign, just can't win an argument like that on the spot with a cop and like the rest of the world, some can be a little, um, cranky.
Plus I suspect they must get a lot of grief. After getting a speeding ticket (deserved I might add) a while back after it was over the cop actually thanked me for being so polite so I figured he must not get a lot of that.
Didn't have any influence on me getting the ticket, but there are so many laws I suspect he could have started finding additional infractions if he had a mind to.
Believe it or not, most cops have already decided what action (Ticket, warning, etc) they are going to take before they even speak to you. They base it on the severity of the violation and whatever department policy is.
I have given some real loudmouthed a##holes warnings because that was what was warranted, regardless of the attitude. Most cops actually stick to that.