Thanks for your input. I think that, if anything, what you're saying strengthens my point. Supplementing with additional vitamins is all well and good, but it does imply that plant-based foods don't provide all of the nutrients we need on their own.

To me, what you're suggesting -- a mostly-veg diet where you occasionally eat meat -- is an alternative to strict vegetarian or veganism that would probably be more accessible and more feasible for a lot of people.