Having lived through both eras, my observation is that the present socio-political environment is far, far more divided now than it ever was in the late 1960s/early 70s. I'm friends with a few Vietnam vets around my age (mid-70s) and they all see now, and saw back then, how the Vietnam War was a disaster and a mistake, as did pretty much everyone else. There was not really a great divide in the country during that time. And as I said, in the military were college educated people, as well as the underclass. There were people of all types and backgrounds. It was not like today at all wherein the military is made up mostly of the so-called underclass. So, in my view today, we have become a much more divided and balkanized country, and the whole feeling is way more of a chaotic shit-show than it ever was in the 60s.
So, getting back to how this relates to city planning and development, I'd say the way to help mitigate this current divide is to continue developing mixed-use residential/retail/commercial, with a portion of the residential units designated as subsidized rents for low-income people. Build these types of developments not only in the inner cities but also as TOD in the historically affluent suburbs. And yes, build these on a street grid of through streets to serve as a platform for walkability, diversity, inter-cultural communication, and openness.