From my experiences.....
The TD must take care of the umpires, especially when it is very hot. Umpires work for the TD. As in any line of work, if an employer puts employees out in the field without support, then you will see failure.
Imagine yourself out there on the field, 90 degree plus temperatures, dusty, humid. You are miserable, no matter your normal temperament. Now throw in some know-it-all parents who have never been in your situation. A perfect recipe for the evolving of a bad temperament. It will happen.
But, if the TD were to ensure that the umpires have plenty of cold water and maybe a cold wet towel to wipe their faces, then maybe everyone would have a more enjoyable game. Heck, why couldn't the parents do this? It would be human decency, wouldn't it? I'm not saying do it 100%of the time but what would it take for someone from the side to reach into a cooler and pull out a cold water for someone who is very hot??? This doesn't mean that you will get a close call, but it sends a signal that everyone (the girls, coaches, parents, and umpires) is in this together, through thick and thin.
Not just umpiring but any worker who sees that his employer or customer is very appreciative of his/her efforts will go the extra mile. In any field of work, you will have employees that just don't care but I think those are well outnumbered by the employees that really care about putting a good product out there.
Just a thought.....