As you say, they are fundamentally the same argument, except for one thing.

A water company that decided to cut off water to people that its CEO doesn't like would, in short order, have to face both political scrutiny and the proverbial torches and pitchforks, if you will; unlike speech, if the water goes away, people start dying or they are forced to leave.

Speech is necessary, but it's cheap as dirt, and most people don't have a lot to say in the first place. If the speech started going away, even in ways that are fundamentally unfair or flaunt the ideals of the country, not enough people would make a fuss about it. You won't die without speech. It can be comfortable to live without speech, or freedom of speech, anyway.

Otherwise, the argument is the same and, in either case, regulation and the pissed-offedness of the little guy could change the outcome. Such is less likely in the case of speech.