The cash position of the church and the employee come out the same, but the tithe is paid and the taxable salary reduced. Pastors don't have to pay as much self-employment social security tax. Other employees and the church pay less withholding taxes and income tax. For openers, the IRS has not approved it. That should be the end of the discussion.
Some denominations impose a tithing requirement on ministers.
Occasionally a church also requires tithing from lay employees. More commonly, an employee's giving practices are subject to a cursory review based on the completion of an annual report. An employee is hardly ever dismissed for noncompliance. Only if an employee is required by contract to tithe, the regulation is enforced based on periodic reviews, and employees are dismissed for noncompliance would the pretax treatment of tithes be appropriate. Improper use of fringe-benefit plans .