Great point
That is very possible (neighbor’s grass etc.), Philip @petussing, and always great to hear from you. 
However, as you say,
But that did not happen. And this seems to be a pattern in economics. I remember the outrage I felt when I was an undergrad upon discovering Sraffa’s claim that neoclassical theory determines incorrectly the profit rate. The model leaves it undetermined, he explained. Of course, in the real world we see a determined profit rate. It follows that it must be determined outside the model – in the world of wielding power to appropriate a bigger slice of the cake. Historical data on profit rates seem to be compatible with a political determination of the profit rate.
My outrage was because economists saw this, and simply shrugged it off and carried on. And that seems to be a pattern. It goes like this:
NEOCLASSICAL ECONOMISTS: Here’s a nice, elegant model. It says that the economy rewards us on the basis of our productivity.
EVERYONE: Nice! But your assumptions are bizarre (Murray Gell-Mann: “You guys really believe that?”).
KAHNEMAN AND TVERSKY: Yep, assumptions do not stand empirical tests, even in the lab.
POLANYI: That model never existed, and can never exist. Human societies treat it as extreme dislocation and react by producing fascism.
MAUSS: Hm, interesting. Why is it that people find this thing so unfair and intolerable? And what would a fair model look like? Let’s develop one!
KEYNES: Your model leads to disastrous policies.
SRAFFA: Even in pure theory the model is inconsistent.
NEOCLASSICAL ECONOMISTS Lalala we cannot hear you we go right ahead.
Now this is unscientific. This is betrayal. It’s as if 16th century astronomers had looked through Galileo’s telescope and decided to ignore what they saw. Which, actually, they did, and then they got Tycho Brahe proposing an earth-centric cosmos where planets move on all kinds of supercomplicated curves to reconcile observation with the untouchable truth that Earth must not move. So maybe we are in Tycho Brahe economics right now. Certainly Ole Peters thinks so, and it is hard to argue with his statement that “if you need to invoke two hundred biases to reconcile your theory of rationality with the data, you probably have a wrong theory and should start over. It sucks for you, but it’s how science is supposed to work”.
I am not qualified to judge Graeber’s work. I use him as a popularizer: I realized keeping in my head a history of economic thinking perspective helps me, a lot. But, like @atelli here, I see no contradiction between being an activist and doing science: Bertrand Russell and Einstein were activists, and used their prestige to push denuclearization, involving Born, Pauli and others. Hirschman himself worked on the Marshall Plan from the background of a German Jew that had been part of a clandestine network smuggling Jews out of Vichy France. All cool people in my book.