Sunk Cost? Also, Tsuyoku Naritai - we can do so much better with the knowledge currently available to us.

It's a quote against which one can test their rationality, maybe?

• When someone died or when it was made has no relevance; only its merit in guiding a government is relevant.
• Their moral and political views don't matter either, unless contained in the present US Constitution; this seems like argumentum ad hominem at first glance, but one needs to check the claim before evaluating its persuasiveness.
• One must argue that knowledge of modern America confers enough of a benefit to forming a working governmental body that scrapping and rewriting the entire U.S. Constitution is preferable to the amendment process.

In an effort to steelman: perhaps the Professor meant to indicate that with the advent of the internet, a representative democracy is no longer the most effective means of running a government by the people, for the people, and of the people. If he was feeling radical, he may have been hinting at how political science has developed as a discipline since the Enlightenment era when the principles founding the U.S. government were theorised; perhaps the best solution is a flexible one, able to adapt to the political system most effective at running an efficient government while still remaining resistant to tyranny. Exempli gratia a futarchy for four years, some form of crypto-direct democracy for eight years, a modified version of Finland's government for ten years, etcetera.