Subjective but not Arbitrary

Just because there are different perspectives, with no way to determine the optimal, does not mean that all possible perspectives are equal and that perspective is arbitrary.

Practical example:
The exact form of education in schools. Pupils have different ways to learn most effectively and the teachers have limited resources to vary their teaching. It may very well be that using any particular form of learning is inefficient for most pupils.

It is a mistake to believe that because of this: Teching methods are arbitrary.
Clearly it is a bad idea to (for example) punish and reward pupils solely by random chance, as this encourages no sort of behaviour and leaves all pupils in a state of passive feeblemindedness.

While a cynic might argue that this might be the objective of a given sort of society; this would hardly count as anything like a school as we know it.