Free trade means that the group or people that can do a job the most effectively are the ones who will do it. While it sounds appealing to voters to protect certain domestic industries, the disconnect in their thinking is clear fairly quickly; if people truly valued that industry's products above all others, that industry wouldn't need protecting to begin with. If a new industry can only survive because of legislation hurting its competitors, all that the law is ultimately doing is delaying the advancement of the superior company, at the cost of tax payer money and lack of opportunity of access to said technology.
An infant company should be protected for a certain amount of time that way it is not swept away by a more established company that knows all the ropes. If we do not shelter to some extent than monopolies will form and that will ruin the economy as well as cause rates to sky rocket without anything that anyone can do.