A team in a hurry to get their warm ups in during a tourney is not trying to disrespect you.
The 3rd team organizing themselves on the field to do warm-ups while the other team is collecting themselves is not the "disrespectful" part of this scenario. In fact, warming up in an efficient manner is most likely recommended to keep games on schedule.
The manner in which they put themselves on the field is the disrespectful part (to me). You now have 24-28 kids & coaches maneuvering in or out of one dugout. I would imagine a few of the kids packing up had a good mind to say "Um, can you wait?"
In fact...going through the dugout probably slowed the 3rd team down of getting out to the field. You either wait...or enter somewhere else.
I agree China...the parent was out of line.