Nobody is forcing anyone to buy anything.

In the given example, is the gas station not forcing Customer B to purchase more gas than they may want or need? What if I have a chainsaw with a 1 gallon fuel tank? Now I need to not only buy more gas than I can use, but a container to safely store it in. (It's also illegal to dispense gasoline to/from an unauthorized container!) Now if I use my chainsaw once or twice a year, I also get to dump out that extra gasoline because it's gone bad by the time I need to use it again.

That doesn't prevent harm to everyone it just allows gas stations to use a single pump and shift the liability onto consumers.

That's a pretty stupid comparison. These aren't prepackaged containers, and that's a pretty key part of the terrible point you were trying to make.