I don’t think anyone is saying cavity searches are uncalled for in all cases - but to do so at the side of the road is in nearly all cases uncalled for, especially in a case like this. She was accused of putting pebbles in a mailbox, not threatening to blow up the post office! In a case like this, it is almost always a tactic for humiliation and domination.
Sounds almost like they were trying to terrorize her and her family.