Nothing in this chapter shall be construed to repeal any existing laws or statutes which exempt or exclude insurers from the payment of fees, taxes, or licenses other than the tax imposed by this chapter. Without limiting the generality of the preceding sentence, insurers upon which this section imposes a tax upon their premium income or in lieu thereof, shall be exempt from income taxes imposed by the State of Alabama under the provisions of Chapter 18 of Title 40, or any other similar law.