They did have permission to fire back if fired upon and they did. You can believe what you want, I don't know how old you are but I lived through those times and I can tell you it was a planned riot with the purpose of making the military look bad and play into the "get us out of Nam" BS meme.
Me too and I was just a dumb teenager at that time. It was obvious that SDS and other subversive groups planned all of these events even to me then. Wonder where the POS Bill Ayers was that day.