Commentary Dozens of big corporations, including Nike and FedEx, have paid no federal income taxes for years, which is prompting Democrats to introduce a minimum tax on earnings. While the concept is alluring to many, tax policy experts are increasingly warning of the undesirable outcomes of the proposal. President Joe Biden’s nearly $2 trillion social and climate spending plan calls for imposing a 15 percent minimum tax on the book income of corporations that report over $1 billion in profits. The change would apply for tax years beginning after Dec. 31, 2022. The proposal, which is in lieu of a higher statutory corporate tax rate, seeks to prevent widespread tax avoidance by large corporations. And it’s popular among voters of both parties, as many people think it’s absurd that a pro-China company like Nike gets a free ride in America. Companies can take advantage of a host of deductions and exemptions in the tax code, which …