Ok, this is me reporting back. Based on the few minutes I was willing to spend on this, and the data sources listed below, I've come to the conclusion that I was wrong about the word "consumer" being widely used where "citizen" should be. I looked at a few dozen usages of "consumer" and they were all appropriate, i.e. in sentences concerning some sort of economic consumption. I hardly saw any borderline cases, and even those were not misuses of the word so much as encroachments of the economic domain itself into areas it didn't use to dominate.
One can still argue about the status of the concept "consumer" in our society, but that becomes a much more subjective thing without tangible linguistic evidence to point to. I'd be interested if anyone has further ideas about how to test this.