Should we protect dying industries?

One deceptively simple economic insight tells us that firms cannot sell things for below they cost to produce and expect to remain in business for long. Yet there could be cases when it is beneficial to society for "firms" to do that - scientists, for example, did not in the past sell much of anything and incurred enormous costs. There is an external benefit to their work, as there is in the work of all of us, especially academics.

I'm wondering whether these arguments could be used to justify supporting a dying industry in a national economy through tariffs or subsidies. It seems to depend upon the industry, but what industries really have that much external value beyond their capacity to produce? (I'm assuming that we can get whatever they produce at the exact same quality somewhere else for cheaper - a major assumption). Does working at a factory really make a man a better thinker? Does the factory improve the environment? Are these people happier and better citizens when they have a decent blue-collar job?

It seems hard to decide, but I think that on the net a low-tech manufacturing firm does not produce external benefits. The money that is saved by allowing them to go under through the market can be funneled back to them while they look for new work. They are now free to retrain themselves as well as perhaps enjoy more leisure (sit around on the internet?).

What about high-tech industries? Again, I think on the whole the external benefits don't justify protecting the industry - but we should be able to compete in the high-tech industries, and we do. We have a high-skilled labor force, lots of capital, and a fair amount of innovation. But we won't necessarily have the most high-skilled workers in the future. Wages will begin to equalize across the world - wages are already skyrocketing in India. Outsourcing won't be cheap forever. By the time this happens we may as well have one world government.