I feel like you are intentionally being obtuse. If you are in a marching band, formed up into a parade formation, and given the command of forward march, you stay in formation and follow the leader and take commands from those who are in charge. This is almost certainly what happened with the Iowa band that night.
If you are just told "get yourself back to the bus", then yes please go ahead and go by ones and twos and walk however you want and get to the bus.
Yes, the individual members do have the responsibility to not hit people with their horns and to be polite and respectful. If I was in that formation, I would have played quietly or not at all and I would not have hit someone with my horn, but I also would have politely but firmly blocked anyone from entering the formation. They do not have the responsibility, nor is it reasonable to expect them to peel off by themselves while marching in formation and try to get to a location they may or may not know.
At this point, it doesn't really matter and I really don't understand the hatred a handful of you seem to have for college marching bands. A handful of band alumni are on here trying to help people understand what is and is not normal for a college marching band so that we can sort out what the Iowa band did that was wrong and also point out which of their claims are BS. We all just want to criticize the right things together. Much as I hate the hawkeyes, I'm not going to criticize their band for doing things that any normal marching band would do. I will criticize them only for what they did that was wrong and inappropriate.