'Crumb'

In the documentary, Robert Crumb talks about his father being disappointed that his three sons didn't turn out to be tough, manly Marines and were instead comic book and art geeks.

This is supposed to be some kind of criticism of his strict, former Marine father, who, according to the film and Crumb himself, worked with corporations on how to motivate salesmen.

I don't know why the Crumb father would be disappointed:

One son, Robert, is a sexist, racist comic book artist, who is an anti-social neurotic, who is self-admittedly unable to love.

The youngest, Maxon, is a neurotic artist, who lives in a San Francisco hotel.

The oldest son, Charles, committed suicide at age 50 after dealing with deep and scarring psychological problems and living with his mother in awful physical conditions.

I don't know why their father would be disappointed. Seems like they're upstanding citizens.