Protectionism is a classic "tragedy of the commons." A select group of beneficiaries profit from reduced competition, while the rest of the country pays a higher price. So it's nice to find a study quantifying the damage done by keeping out imports. The Commerce department looked at the impact of sugar import barriers, which raised the commercial sugar price from $0.109/lb (world price) to $0.235/lb (US price). They estimated 10,000 jobs were lost. They pointed to a Life Savers factory getting moved from Michigan to Canada, so there's some specific people who've been hurt by protectionism.
Hopefully this example will help change some minds in the next free trade debate.