I was not an ROTC cadet, but I've had a few negative experiences with reactions to my uniform.
Across the street from the Coast Guard Academy is Connecticut College, Conn College we called it. One day as we were, playing sports I believe, on the parade field (part of the Academy that faces a main road), a Conn College student on the other side of the wall marched by screaming "Seig Hail" (Don't know if I'm spelling that correctly, and I took AP German...). He continued for probably 30 seconds until a growing group of Coast Guard cadets made their way towards the wall...the kid picked up the pace quite a bit and stopped the Nazi hand motions...
That's right up there with a popular rumor that "way back" while some fairly liberal Americans were protesting at the front gate of CGA, the Regimental Commander about-faced the Corps of Cadets, fixed bayonnets and marched (if not charged) the front gate...and scattered the group. I'm not advocating violance directed at Americans excercising their right to assemble, but in an "Us v. Them" mindset, it is a "nice" story. I would not recommend this course of action however, the rumor was followed up with information that many demerits had been given out after the incident.