It's also true that there are good reasons not to let your farming industry completely collapse. Aside from the obvious large numbers of people who would lose everything. It's in the best interests of the US that they can feed themselves.
In general any nation would want to be self-sufficient in all basic necessities, that would come under threat in war time.
Every protectionism is different because ... reasons. There will always be an "what if..." to justify everything.
Other terrbile side-effects of our agrisubsidies include crap processed food, agricultural practices built on assumption of nearly free water leading to droughts, nutritional deficiency in produce etc etc.
Exporting food for free is a more complicated topic, on the imports side, protectionism is justified for critical functions. If we outsourced our food production, we could get it more cheaply (it's already cheap), but imagine if a supplier suddenly decides to cut us off? Food security is a national security priority moreso than typical military stuff like steel mills.
Then don't complain about other countries' protectionism. They also have the right to decide what is critical to them, right?
> my guess is that if [...] had been more successful, China would have put a Mao-sized thumb on the scales.
This is how it lost me, it shows how light he is on facts.
I do agree with the 2 statements "China is protectionist" and "protectionism is bad".
But I am cynical enough to see that everyone carefully pics which protectionism they complain about.
As a Brazilian I am still waiting to hear Americans, Japanese and Europeans complaining about their own farming protectionism, at least as loudly as they complain about other countries.