What a fantastic website.
Probably a difference in human and emotional education. Times were slightly rougher in the 60-80s.. people may have had thicker skin and more social skills.
All in all it might just be a natural cycle of sclerosis, not help by the internet amplifier.
ps YouTube suggested some letterman shows with meg parsont (a random employee working in front of the studio building) I felt Dave was a bit intrusive if not bullish on her. Made me feel conflicted, as I hold the dude and show very high in mind.
Never followed Letterman's work as I never found him funny and it always felt like a used car salemen's type shtick, I was more likely to watch Jay Leno due to him being in LA and loving cars. Honestly Simpsons or Married with Children re-runs were more entertaining than both to me...
But, I watched that Comedy Store documentary from last year and heard from guys like Chris Rock in other interviews throughout the years that Letterman was generally known to be a total miserable grump when not on stage.
His persona and his real life demeanor were 180s of each other, which kind of makes sense the more you learn about how messed up psychologically and emotionally comedians often are and given how much time the spent on Freddy Prince's suicide, it really drove the point home that they are often just broken toys with a narrow focus on doing something to east their deep pain. And Letterman was from that era of comedians and was around the store back then.