“It sets an awful precedent if granted.
It makes the IRS a political investigation arm.”
For a change?
It would mark an expansion of their power.
Currently, the IRS can be all over you about deductions or tax status (like Lois Lerner was), or your past tax bills.
But, this would let law enforcement use all of the accumulated IRS information for the purpose of investigating other past actions than financial/tax reporting. If they can do it to the President, for transparently political reasons, they’ll be able to do it to anyone, in time. Slippery slope.
In the non-financial area, FISA was supposed to prevent, or at least control, weaponized surveillance, a different sort of privacy invasion. It looks as if the FISA process was defective in its relation to the President. Do you think that you’d get less deference from any court-mediated violation of your privacy, whether for communication or for IRS filings?