My first question would have been to repeat what the cop said to me. In other words, I would have asked, "Is the only reason that you are stopping me is for open carrying?" As soon as they said, "yes", I'd let them know that they do not have the authority to do that and if I'm not being detained, then I will be on my way. If they then said that I was being detained, I would ask for what reason. If the cops every say because you are open carrying, go back to the fact that they do not have the authority to do that. Close, to what Hoss said, but not exactly.
Anyone who carries a firearm (OC or CC) needs to know case law Terry vs. OH. From this case, a police officer cannot detain you unless their is reasonable suspicion of committing a crime. Walking down the street open carrying in an open carrying state does not give LEO's reasonable suspicion of committing a crime.
However, loop holes do exist... if there were shots fired recently in that area and you just happen to be there... there's reasonable suspicion (RS)... if there was an armed robbery that happened near there, RS.... if any other crime happened near there recently with a firearm, RS. Therefore, if the officer that stops you doesn't give any sort of reason other than the fact you are carrying as the reason for your stop, throw Terry vs. OH at them and let them know they do not have reasonable suspicion to detain you and you will be on your way.