Suppose that ABC corporation has issued stocks and bonds. The stock's symbol is ABC. As a shareholder, you are an owner of the company (albeit, a very minor one). Now, suppose that you lend your own company, ABC, some money in the forms of buying ABC bonds. As you know, when you purchase bonds, the money is borrowed from you - the investor - and they pay this borrowed funds from you in the form of interest.
Because I'm investing money into my own company, this is an expense, which is tax-deductible. I should be able to invest in corporate bonds on a pre-tax basis. However, the interest should be taxed, because this is, for sure, earnings. Also, the interest is not taxed to the corporation, but using my logic, it should be taxed to the investor (which it is), and the money to invest in the bonds should be done on a pre-tax basis (which isn't the case now).