Is there a tactful way to "get arrested" when the officer said he wasn't going to? I can see them tacking on some sort of interference charge or something else that will stick even if the OC one won't, though it would be an easy argument that they led you there with the false charge of illegally OCing. Are police allowed to lie to you even when you've done nothing wrong? I understand they can say Billy Bob said you were the trigger man, but can they walk up to you and say you're doing something illegal to fish and see if you'll admit anything?
The video recorder in your cell phone is your best friend in this circumstance.Just don't wait until "after the event" to start it up.