> He fundamentally does not understand how markets work. I am a software engineer.
I can assure you that the Harvard and Yale educated professor that's written textbooks on the subject knows how markets work. He might be heterodox in his adherence to marxist economics, but he fully understands the orthodox position, almost certainly in more detail than you or I ever will.
> My question: an oft repeated refrain, when Marx is touted as a reasonable alternative, is that any time anyone tried his ideas out, it was a total disaster (Stalin, Mao, Pol Pot, Chavez).
A couple things. Chavez is of a different category from the other three just on the amount of death under the other regimes. The question of the results of socialism and capitalism is complex. It's worth reading both historical and economically focused works to get a more nuanced view than the one that you've laid out. For a few suggestions:
On historical critiques of the US-centric perspective:
The Jakarta Method, Vincent Bevins
The Darker Nations, Vijay Prashad
A People's History of the United States, Howard Zinn
Economic works:
Competing Economic Theories, Richard Wolff
Seventeen Contradictions and the End of Capitalism, David Harvey
There are more authors (Kliman, Moseley, Shaikh, etc.), but these two would be a good start.
These are works with particular perspectives and should be read as such. If you want competing ideological works, read a standard history book and Hayek, Mises, Friedman, etc.
I'd second the other response's recommendation of Richard Wolff's work. He's a marxist and democratic socialist, so read his work understanding his perspective in relation to your own, whatever that might be. That being said, I found his book Competing Economic Theories on neoliberalism, keynsianism, and marxism to be very fair to all sides.
Claiming that something is right because it exists as it is under the current system without further justification is equally, if not more short sighted. It's where "plainspeaking" and begging the question combine into a kind of catnip for people that want reinforcement for their impulse towards the status quo. I'm not familiar with this particular quote, but I've read one of his recent books and it was full of this sort of thing.
https://en.wikipedia.org/wiki/Deadly_Games_(film)