Under the law, tax-exempt entities such as your IRA are not tax exempt with respect to unrelated-business taxable income. In the first point that you are trying to make, you are essentially trying to assert that the unrelated-business taxable income is not unrelated-business taxable income. With regard to your second point, yes, the UBTI is effectively being double taxed, but not twice to the same entity. Your IRA is subject to tax once and you are subject to tax once.
