It is not always easy to make a 'call' ...especially a correct call.

Often umpires will meet, privately off to the side.  They may disagree on the call, but they will discuss it, and together they will present the decision.  They do not discuss it with anyone else ...it is only discussed among themselves.

Parents often do not agree with each other on decisions they have to make, yet they should consult each other privately. And whether the call is the correct call, or not, a consensus of one decision should be presented.

There should be no 'one-umpmanship' going on between parents.

If this approach is followed, then everyone will have a 'sporting' chance.