Well, nobody will ban products from other countries just because people would be forced to buy local products. The reason I gave was to promote domestic industry. And I do think that having a strong, independent, domestic food industry is a good thing for any country.

Here is why:

1) Food is a necessity of life, it's a good idea to not be dependent on imports of such things for many reasons.

2) Most common food products (like cheese, milk, bread) are fairly easy to produce anywhere in the world. This is not the 15th century where not everybody had the skills, technology, and where climate mattered a great deal more.

3) Efficiency is more and more important every day. Local goods require less transportation, less storage, no tariffs, do not depend on inter-state relations. Efficiency is not only important economically, but environmentally as well.

4) The government of the country has more control over the products that are produced there. This means it is easier to enforce health and quality standards that exist in the country.

that makes your legitimacy go down and would hurt in other economic areas too

I'm not exactly sure what you mean by 'legitimacy', but I am of the opinion that the government of a country has the obligation to work to improve the quality of life for its own citizens and worrying about 'other economic areas' is secondary to any issues that may exist in their own country.

The aggressive push for 'free trade' and laissez faire capitalism in what we now know as the third world is what created the terrible conditions in those countries in the first place. The prosperous western countries have A LOT more trade and domestic regulations than any third world country, and the recent protectionist policies in China are one of the reasons why the standard of living there is slowly improving.