Student or Learner
Can we use 'must' in past tense in this manner: Society had reached a stage where it must respect workers.
I know must is normally used in present and future tenses, but here in past perfect, it seems to be the only option. 'Must have' won't work here nor will simple past such as ... it respected workers.
Am I right? Or, would it better to use 'should' or 'ought to' in this case?