This is the first Nixon-Kennedy TV debate from 1960 (The first time presidential candidates ever debated on TV). I'm no great fan of either JFK or Nixon. But it's notable that the debate is a lot more substantive than what we saw a couple days ago.
And the difference isn't just about Trump, egregious as he is. Since 1960, there has been a gradual decline in the substantive quality of these debates as candidates and their advisers gradually came to realize that you can more easily woo a largely ignorant electorate with crude sound bites than with substantive arguments.
That said, I don't want to suggest that the Nixon-Kennedy debates were truly at a high level. There are lots of crude fallacies in their arguments. For example, in this debate both make liberal use of the trope of crediting or blaming the incumbent president for anything that happens during his term, regardless of whether he actually did anything to cause it (or could have avoided it). But, for all their flaws, the 1960 debates were on a substantially higher substantive level than more recent ones.
I would add that the media people asking questions also asked a lot of good ones (e.g. - the one about why farmers can't get along without subsidies and price controls, just like other businesses do).
JFK and Nixon weren't necessarily more moral than current politicians. They just hadn't (yet) figured out the format, and what you could get away with in it.