You can't tell by looking at someone whether they are going the speed limit or not? There is a BIG difference in a car going 45 verse 85. Even without your true speed, which he may have, you make no mention of radar, he can still cite you for excessive speed, speed unreasonable or reckless driving (a crime in many states) He could have had radar on, if he was driving, he could have said "oh, gee I'm doing 45 and that guy is going WAAAAYYY faster...duh, let me stop him"
Bottom line, you admit to speeding, you where speeding, he said you where speeding...so whats the issue???
Cops are trained in VASCAR, a speed estimation system. It is very effective and is actually the legal way radar/laser works. Cops are supposed to visually estimate your speed and them confirm it with the radar/laser.
I was trained and was amazed at how accurat it really is. Even without training, the average person can estimate a cars speed pretty good.
We all know what 45 is and what 45 is not. And its not 85.
Sounds like you got lucky. Whats your complaint, exactly?