You would first need to have a right to political speech on other people's property for them to violate. You do not have that right to begin with.
ok, so you really don't know what the state actor doctrine means...gotcha.
Brentwood Academy v. Tennessee Secondary School Athletic Association, 531 U.S. 288 (2001
"The nominally private character of the Association is overborne by the pervasive entwinement of public institutions and public officials in its composition and workings, and there is no substantial reason to claim unfairness in applying constitutional standards to it."
[12] Part of the basis for this determination were historical statements by the Tennessee Board of Education, which had granted regulatory authority to the association and recognition of its own independent authority. For example, the Board explicitly approved the TSSAA's rules and reserved the right to continuously review them in the future. Further, employees at the association were given state pensions. Because the association could essentially "coerce" the member schools to follow its rules and the state would back it up, it was using state
police power.
[13] Therefore, Souter concluded, the restrictions on denial of due process would apply to the association, and the lawsuit could proceed in the lower courts"
Burton v. Wilmington Parking Authority, 365 U.S. 715 (1961)
Also, a close symbiosis was noted between retail businesses having nearby parking and a garage being close to shopping opportunities to the point that they were a "joint participant." Based on the close interplay between the government and the company, the court found that the exclusion of black customers was a violation even though no government agency was directly discriminating: "the exclusion of appellant under the circumstances shown to be present here was discriminatory state action in violation of the Equal Protection Clause of the Fourteenth Amendment.
(Rendell-Baker v. Kohn, 457 U.S. 830 (1982)); , but if the government coerces, influences, or encourages the performance of the act, it is state action