I think historical evidence is useful but I would not rely on it to bolster any arguments for any particular view.

Yet the view that times tend to change, and mores tend to be relative rather than universal across human history, are clearly borne out by even a casual survey of history.

What has happened at various times throughout history might be cited as "the norm" when we would probably know that there were different pressures within that particular society to cause any differences seen in other societies.

Yes, including this one, particularly the pressure to infantalize anyone who is under the age of 18 regardless of whatever their individual merits may be. Which bolsters my main point.

We seem to have glimpses into different eras and the article I quoted was I think representative and sufficiently far back as to do so. You can honestly say modern history is entirely verifiable? Who exactly did kill JFK?

Specific facts may not always be verifiable, but particular era-specific ubiquitous trends, attitudes, and values that are clearly caught and explicated on film or in the literature of the time are often not in question, as the PSA, documentary, and various tomes I linked and mentioned make clear.