U.S. Presidential Signing Statements aren't worth the paper they are written on. Unconstitutional Presidential Directives and Executive Orders are likewise null and void. Unconstitutional statutes passed by the legislature and signed into law by the President are also null and void. The only way the executive branch can become a malevolent dictatorship is by the acquiescence of the legislature and more importantly the judiciary and those in law-enforcement and the military who would support a malevolent dictator over a proper understanding of the spirit of the law.
U.S. citizens have the constitutionally guaranteed right to free political speech. They may advocate for the economic boycott of anything, regardless of unconstitutional statutes to the contrary. If someone doesn't like something some company is doing and he or she wants to tell others that such activities are evil and that people should not buy from the given company, that's that person's right to free political speech. This of course includes those who advocate for the peaceful abolition of inhumane treatment of animals by corporations and others.
If the judiciary, legislature, and law-enforcement and military all go along with the creation of a malevolent dictatorship under the President of the United States, then to hell with them all. They will fall by the force of the righteous spirit who does exist and who has intervened before and will do so again. The protection will be lifted, and Satan will come to devour his own.