As with all things involving people, how you are dealt with depends on who you are dealing with. I'm confident at some checkpoints one may have to deal with aggressive jerks while at others there are good people. I've cycled through the checkpoints south of Tucson several times. I'm 63, ride a carbon fiber bike with no gear and have a white beard that makes me look my age. I roll through in both directions without even stopping although once I stopped to obviously photograph the checkpoint well in view of the agents. No problem. They saw me go out then back in and I'm sure that helped with their decision to not even bother to stop me. Had I been dark skinned I'd bet I would have been at greater risk of being questioned as would having full panniers I'd guess. I don't carry any ID when riding. When touring I do. I do know from long experience you can get through checkpoints much easier when you are friendly and cooperative. Nothing wrong with choosing to stick up for your rights and refusing to talk but there can be a cost to that course of action. I find the checkpoints to be hideous and ineffective and intrusive.