Kind of a weird form of speech. People under 18 can’t engage in it, felons can’t engage in it, non-citizens can’t engage in it. A vote cannot be spontaneous, it only happens when the government says so and puts into action a pretty cumbersome process to monitor and regulate it. There are specific laws dealing with voting that are not intermixed with laws on speech. Also, it is generally thought to be private, just between the voter and the ballot counters, as opposed to being a matter of exercising the press or religous liberty.
I don’t think speech is the correct way to think of voting. I’m not sure there’s a term for it, but I’d say “civic duty” is a better description of voting rather than speech. If I think of other civic duties, it is a short list of things, and it is absurd to think that people should get paid for those: should attorneys be able to pay jurors personally for their time? Of course not, it is ludicrous.
Moot, not mute.
This argument to me is like saying, “I already do something unhealthy, I drink a sugary soda every day. Since I’m already doing unhealthy things, I might as well take up smoking.” Well, no, drinking unhealthy soda does not mean that smoking is okay. I think Citizens United is a disaster, but that doesn’t mean that we should adopt bad laws because some line in the sand has been crossed.