Life in the incomprehensible future -- a classic scenario

It is a scene in many a time-travel novel.  Boy genius, who works in his secret lab, creates a device that will take him to the future (he's not interested in Julius Caesar or even Cleopatra).

So he goes to the near future and finds that it's pretty much what you'd expect, with a few inventions more or less.

Except...

There is one cultural or religious or social innovation that absolutely shocks the boy genius and his friends.  How  can people who are otherwise so much like them think/believe/do that? B.g. flees to the farther future where a certain normality has been restored.

It occurred to me a little while ago that we have -- many of us -- crossed over such a line, and would deeply  shock time travelers from the near past.

Why so?  Same-sex marriage.  We are the weird ones, no matter who we are married to and the b.g. can't get over us.