Donald J. Trump had originally requested secret service protection to avoid assaults from Joaquin "El Chapo" Guzman. Mr. Guzman has, since Trump's request, been back in Mexican custody. Therefore, in the interest of tax payer funding, the government no longer owes a duty in providing safety to Mr. Donald J. Trump. He is a self proclaimed billionaire who can fund his own security.
Secondly, in light of the disturbing events occurring at Trump rallies, including the Chris Morris, a.k.a. -Times photographer incident, it is fair to say that this would be an inappropriate use of federal tax paying dollars.
Lastly, the U.S. government doesn't owe a duty to any one particular high profile, wealthy celebrities. It owes a duty to the President and Vice President of the United States.