Our experience last Thursday on a MM day was actually very civilized compared to what your are describing. Please note that on that MM, there were no pre-line.
We got at the gate at 7:20 for a 8 am opening. We were probably the 6th family in our row. Then they opened the gates at 7:40. My 2 daughters walking (on the left side of the hub) quickly - but not running - and we were right on the rope at the end of main street.
At that point, we made a plan for me to walk quickly to the Anna and Elsa meet and greet and my daughters would follow. When the rope dropped at 8 am, I again went to the left and through the castle very quickly. My 2 daughters were following behind, but the plan was to meet up in line. (Before you get scared, my daughters are 16 and 7). Well, there was a few of us walking very quickly as the cms were telling or stopping those that were running. Along the way, many cms with Anna and Elsa cards were pointing the way, but really, monitoring the situation.
I actually got there third in line ... But got scared and let a few people pass by because my daughters hadn't arrived yet. We ended up 6th in line and had met both princesses by 8:15.
Everyone on that day was very behaved, and everyone was closely watched by a bunch of cms.
But no pre-line (we saw the pre-line on another day and we were surprised to see that there were none on MM day).