I think that's exaggerating a fair bit / losing sight of the complexity of how repression has tended to work. As far as I can tell, assassination is usually not the go to for rhetoric alone, within the US itself. Most likely, in the scenario of electoralism and from the starting point of trying to get elected, he'd get shut out of interviews more, like what happened with Bernie Sanders. But if he was polarizing and charismatic enough, and utilized his own media to help gain popularity, they'd be tempted to bring him on shows anyway for the views because $$$. If he started gaining too much traction, they might go for imprisonment, like with Eugene Debs of old (but this could also be leveraged to radicalize more people). If he was openly organizing in a militant way, like the Black Panther Party of old, then I'd more expect him to need to have bodyguards and such (but then electoralism would be more a vehicle for education than a serious goal to get elected).
So yes, there is varying degrees of risk involved in being openly opposed to the empire's narratives, but people should not be paranoid that any word said against it is going to have a sniper trained on their position. The empire is a) not that powerful and b) not (yet) stupid enough to think that's necessary to hold onto power.