"Simply playing by the rules". No they aren't. They are paying a small fortune to figure out how to avoid paying taxes by following the letter of the law. However they break the spirit of the law, and hence are not playing by the rules.
This is not different from using drugs to win sports which hasn't yet been banned because it is too new. Strictly speaking it is legal, but it is both immoral and unethical.
The problem with depending on every possible behavior being described in the law and closing every loophole is that that would create a very draconian legal system nobody wants.
It is the same as with contracts between two parties. It is easy to screw each other over if one nitpicks about everything and don't follow the spirit of the contract. However the problem with such behavior is that it dramatically increases transaction costs, because one can not trust each other and have to make extremely complicated legal contracts.
I've noticed when dealing with American how the lack of any trust, makes any kind of business deal very expensive. Contracts are completely over the top.
I don't think this is how one wants society to develop. Parties in an economy have to be able to play fair with each other most of the time without resorting to ever more insane details and regulations.