" It took the nation a long time to come to the realization that that war was unjust,"

That's not why we quit/lost Viet Nam. We didn't come to the realization that that war was unjust. We came to the realization that it was not win-able.

When the numbers of people who realized that it was unwinnable (and therefore a waste of their men's lives) grew, and joined with the few who thought it was an unjust war, the war was brought to a close...

...and a renewed slaughter in Southeast Asia began.