On the other hand, your use of descriptors such as “American indoctrination camps” and “zombies spouting left-wing talking points” does not make it seem like yo

On the other hand, your use of descriptors such as “American indoctrination camps” and “zombies spouting left-wing talking points” does not make it seem like you’re particularly open or receptive to “spirited debate”. These are not “civil” terms used by someone who is seriously interested in having his or her ideas challenged. From my perspective, it sounds like your friends were exposed to ideas that would have been previously unavailable to them, and having had their horizons expanded, came to modify their views on certain things they had been effectively taught as dogma until that point. Then, when they came back and tried to communicate those newfound viewpoints, they were dismissed as brainwashed zombies who weren’t using their intelligence. I certainly would not consider it worth my time to argue with someone who believes me to be indoctrinated beyond hope and dismisses my intellectual capability simply because he or she disagrees with me.