 If you live in a neighborhood that has a homeowners association that is not a governmental entity, and if that homeowners association has an agreement that you have agreed to abide by when you live there, saying you won't put a sign with the F word in your front yard, there is nothing preventing the homeowners association from doing that. You can't raise a free speech argument because it's not the government trying to curtail your speech. Well, you agreed to also. That's right. You didn't have to go live there.