Iam not trying to defend him jOhn, but was the pa + mixing desk ok??
Was it new to the engineer? (can be difficult to get used to, quick)
Plus if he had more than one band to mic up this can be hard to get right, esp' if your under preasure.
If there where no sound check rehearsals with all the bands, then Iam not supprised at all.
Iam sorry it spoiled your (and others) night. Think how the engineer must feel.