> Corn subsidies are a few billions of dollars a year, that’s pretty cheap for food security.

A few billions a year to destroy farming capacity in the rest of the world, and even within our country for growing anything non-corn (because it has to compete with subsidized ethanol production). You could get more benefit and do less harm by using those billions to maintain production capacity for other crops (even if you're not even growing anything but a cover crop!), plus generate far more energy from solar production.

I'd say it's pretty expensive for food insecurity plus opportunity cost.

> Ethanol in gasoline is food security policy that exists to have something to use the corn for rather than throw it away.

That's just false. The mandate (The Renewable Fuel Standard) forces ethanol production. The law says you have to overproduce. If we wanted to preserve capacity, we wouldn't grow the corn, we'd subsidize maintaining the ability to grow it -- and other crops -- which would be way cheaper and also provide more food security.