Again, we're not taking away from the 60% because again, it's field corn that's being used for fuel. You could argue that that when field corn is used as fuel, it can't be used to feed our livestock as it would normally be used, which could lead to less meat available...but again, we don't have food shortages on the supply side of the equation (which is where that 40% number and mass obesity come in). We have issues on the distribution side (i.e. you have to have money in order to get food and giving away food is TEH SOCIALISM).
As for your field corn response. Again and again, we have no food shortage in this country. We have too much food, enough to feed the world. There's no need to find a way to make field corn edible. If we needed more directly edible corn, we could just grow more sweet corn instead.
The reason these government subsidies exist is to artificially create a DEMAND in the marketplace so farmers (well, nowadays, massive multinational conglomerates) have something to sell because there's only so much natural demand for what they grow. The fact that these subsidies lead to catastrophic distortions in the global market that lead to skyrocketing food staple prices and starving children is apparently a price we're willing to pay.