Rudolph Giulani's argument is, like most other excuses for Trump, nonsense. Giulani argues that Trump is under an obligation to maximise profit for his shareholders. It is true that those in charge of a public company are so obliged, within certain legal and ethical boundaries. But the Trump Organization, Donald's main business vehicle, is privately held. As such, Trump can essentially do whatever the law allows him to get away with. He could even choose to pay tax if he wanted to.