These arguments tend to ignore that a reusable thing is often just a lot better at whatever it does. You can put a few liters of milk in a reusable bag without triple bagging it. You don't have to worry that it will split open and spill out on the ground. You can use the bag to pack for road trips, to store kid's snacks and toys, as a gym bag, etc. Groceries aren't the only thing anyone caries and people go further than between their boot and fridge.

In Switzerland grocery stores have been promoting reusable (recycled plastic) bags for years, and people use them for everything: I saw someone in Interlaken carrying firewood with one.

So:

- To people promoting reuse: maybe go beyond the environmental impact and appeal to quality of life. Having bag or two in your boot all the time is a good idea.

- To people promoting single use: others have pointed out that you need to address the other environmental problems beyond energy, but also acknowledge that you're asking people to find a replacement for their everyday tote bags as well.