This statement may forget in which context protectionism or free-trade are advantageous or ruinous.
Friedrich List defended an educator protectionism for the national economies lag behind the major liberal powers, such as Great Britain. Protectionism is not an end in itself. He believed that each nation had a temporary need for protection to develop, so that its industry become sufficiently competitive on the world market, before free-trade can become the rule. A protective tariff was necessary to increase the chances of survival of young industries.
Therefore, the economic policy must not be the same according to the industrial landscapes. A country which is based on a system of small or medium-sized enterprises should begin with this protectionism. A country which is based on a system of large companies should go toward free-trade.
Then, the issue is to know if our country is more in the first case or the second (I let you do it). The size may be evaluated according to the weight in the GDP, the number of employees, the proportion on all national enterprises, etc.
Then, I suggest you two unavoidable reading tips on this subject:
Friedrich List, Système national d’économie politique, Paris, 1857.
David Todd, L’identité économique de la France : Libre échange et protectionnisme 1814–1870, 2008.