Sometimes the truth about a child's behavior (as the teacher sees it, anyway) can be very confronting to parents. Even when presented with watertight "evidence" of a misdemeanor, I've seen some parents stoically choose to believe the child's version of the event, anyway, because "My child never lies to me". It is almost as though they'll go to any length to hang on to the belief that they have that "unique" relationship with their child. The thing is, the child has fibbed to the parent (for whatever motive) because kids' do fib!
I well remember telling my own parents colourful versions of the truth when it suited me.
Sometimes I got away with it & sometimes I didn't. However, I can't imagine parents of the same generation as my parents automatically refusing to believe teachers & making a huge issue of the child's rights in circumstances like this. I've seen parents remove children from particular schools rather than believe things they (it seems) can't bear to believe about their child. It doesn't do the child much good, I'm sure: no consequences for anything, it seems.