i think it boils down to local situations. i've never been pulled over and have always acted like another vehicle. i stay out of the debris and in the lane, sometimes in the center of the lane. maybe cedar city, utah is picky about cyclists, or maybe someone with political influence is putting pressure on you indirectly, so you may have to stand up for your rights in a mutually respectful way. or maybe you missed opportunities to let shy motorists pass.

at first glance, taking you word-by-word, it sounds like you're not wrong. the policeman's comment about mirrors don't sound accurate, but i don't live in your town. his comments about you staying out of the lane do not fit with what he previously said about staying in the right part of the lane. also, being able to keep up with traffic is not a requirement for a cyclist, because that's usually impossible except in gridlock.

check your local laws, print out the ones that specifically apply to you and keep them with you. if you are stopped again, be ready to politely show them to the officer in a peaceful, but confident manner. still, i don't envy your situation, i've never been hassled that way.

one would expect law enforcement to actually know the laws they are paid to enforce.