Court cases have established that you don't need actual action for a free speech violation to have occurred. The act of using your government position to pressure, coerce, or threaten people who are using speech you don't like is a violation of the Constitution, flat out.
Otherwise the protection of free speech means nothing, because politicians can merely threaten you all day but never pull the trigger on an obviously disallowed act while implying that you'll make trouble for involved actors which has a degree of separation, enough to avoid it being a direct cause and effect. And in this case Carr did exactly that by threatening to make trouble for affiliates like Nexstar -- as long as your threat has a material impact (like causing a company to adhere to the desired action to avoid further red tape in their acquisition approvals), it would be enough to quell constitutionally protected speech.
Otherwise the protection of free speech means nothing, because politicians can merely threaten you all day but never pull the trigger on an obviously disallowed act while implying that you'll make trouble for involved actors which has a degree of separation, enough to avoid it being a direct cause and effect. And in this case Carr did exactly that by threatening to make trouble for affiliates like Nexstar -- as long as your threat has a material impact (like causing a company to adhere to the desired action to avoid further red tape in their acquisition approvals), it would be enough to quell constitutionally protected speech.