Not sure why you are expecting the LEO to know all legal rights specific to a cyclist(or anyone else for that matter)
LEO's are expected to know how to enforce the law. That being said, not one LEO on this planet knows every law along with all the technicalities and legal minutiae associated with it.
This LEO was quite obviously wrong and had a very poor attitude. I hope he learned something from this and would also not be surprised or upset if he was also reprimanded.
What's with all the cycling self pity though?
Legal rights of cyclists? Driving public having no clue? whaa, whaa, whaa.
LEO's pull over pedestrians, motorists and a million other possible offenders every day. They don't always get it right. They are not perfect and there are always variables.
Are you seriously so naive that you think this is some type of cyclist specific phenomena?
A&S forum has a rabid following of cycling crusaders and they can only muster about 6 of these stories a year. Do you realize what a tiny % that is?