If you dig deep enough you can find some sort of ‘bias’ in just about anything. A cultural artifact will reflect some world view. If its too narrow or shallow it won’t endure. Lear later had The Jeffersons which centered around a black racist. You would NEVER see that today.
The Jefferson’s was also created and operated to promote Norman Lear’s leftwing views.
To change the American culture over 40 years took effort, and like Sesame Street, it had to be made to reach into the homes, the messaging is the purpose but it has to be worked into something palatable.