There actually is a religion/practice that eschews even eating whole or root vegetables on the basis that killing plants is also murder. It's called Jainism, and practitioners eat only fruits, leaves, nuts, seeds, and the like. They also walk barefoot, and sweep the ground in front of themselves as they go to avoid inadvertently stepping on insects.
And in countries like India, the belief is neither considered outrageous nor is it hard to follow. In fact, Jain food is readily available and basically the same as typical Indian vegetarian food minus the root vegetables plus replacements. It is often hard to distinguish.
