Seriously, though - ask former President Mitt Romney why we are afraid of tax records.
Oh, that's right - Romney never became president, in part because the Democrats lied about his tax records.
Which is what will happen when the grand jury starts "leaking" phony information about Trump's tax returns, and the Democrats and the Media [but I repeat myself...] start lying about them.
Treasury and Commerce both have confidentiality assurances for a reason.