Should vegan humans eat "dirty" vegetables to get B12?

Vegetables usually have some minimal amounts in them (often produced by bacteria), but when all you eat is vegetables, it's enough. Now days anything fortified, like breakfast cereals,often have enough b12 to rock your world. You would need a lot of insects to feed someone, but I suppose it would be better in terms of animal cruelty to eat insects because they would not be put through as much pain?