I subscribe to the Chicago school way of thinking way more than Marx or Keynesian economics, but I totally disagree. Everything about economics can be wrong. You can't control for every variable in a market. It just isn't possible. Even economic "laws" like supply and demand have counter examples like Giffen goods.

Counter examples only show that something does not work in all cases. It isn't a proof that something doesn't work in any case. Supply and demand is going to hold true in the vast majority of cases despite the existence of counter examples. In a similar vein, you can't say that an economic model is invalid in all cases because there are counter examples.

There are a ton of external factors that lead to the success or failure of a market. Culture, politics, resources, and industrialization play a huge role in shaping the market. These things are ever changing. Argue against the model, not its success or failure.