Forget all the simpering comments about crew and pax, if someone will not follow a legal instruction from a CC member, who is empowered as representative of the captain, then they should be offloaded.
I would say, on the basis of the facts as presented, that this was a poor performance by the CC members - if the rules say rows 1-16, then that is the position and to let someone sit in row 17 is not on.