I come to the same conclusion. I have an alternative protest though. This is something that my wife and I did while saving for a down payment on a house as a money saving idea, but it would work equally well as a protest targeting gas stations.

Buy ONLY GAS at gas stations; No soda, snacks, oil, groceries, light bulbs, coffee, etc. There is nothing in that gas station (besides gas) that cannot be had somewhere else for a better price. Also these sundry items generate quite a bit of profit for the operator and are completely discretionary on your part. While you might be forced by circumstance to buy gas, you don't have to buy sundries.

Dan