They should only be available for small "family" farms in order to keep them competitive with the agri-corporations.
I agree. The large maga-farm corporations can afford to run their operations without subsidies. In order to keep the small-family farms open, either subsidies or competitive agreements between them and food stores need to be in place.
And why do we need to keep small-family farms open?
Elimination of genuine farms (as opposed to factories that produce agricultural products) has (and insofar as it's happend has had) a serious impact on food quality. There are cultural and community issues which ought to speak for themselves and there are also often environmental and animal welfare concerns.
It would be better to eliminate industrialised agriculture.
But if people don't mind the lower quality of food, why should it matter?
As for environmental/animal welfare conerns, they should enact/enforce stricter laws. That seems like it would make more sense than government subsidies.