It does kill less animals. And the consumer of a vegan diet is not paying the farmer to breed up and kill animals. The consumer of a vegan diet wants to be able to buy food that doesn't involve pesticides and other procedures that kill animals and the planet. The consumer of a diet of animal foods is either intentionally killing animals or paying someone to intentionally kill animals. There is a big difference.
A vegan should avoid eating food where the farmer is using pesticides to grow the food, and thus intentionally killing bugs. He/she should opt for growing or buying food from vegan permaculture if possible. If he/she has this choice.
Pesticides killing animals and the planet are used because we are living in a nonvegan world. The person who accepts the exploitation of animals for food is responsible for this. Vegans try to avoid this, but won't commit suicide if this is impossible.
All monocultures are unethical. We should as a moral imperative go over to vegan permaculture, which is sustainable and healthy for the planet.
I recommend this article re. the claim that a vegan diet doesn't kill less animals: http://www.abc.net.au/radionational/programs/scienceshow/vegetariansim3a--less-grains-for-animals2c-less-animals-kille/4679802
Furthermore I recommend this resources which touch on monocultures and other important environmental issues, etc.:
How violence and domestication of animals, leads to violence against humans:
Animal Oppression and Human Violence, by David A. Nibert, Professor of Sociology at Wittenberg University.
The Home: https://www.youtube.com/watch?v=jqxENMKaeCU
Dirt the Movie: http://www.thedirtmovie.org/
Planet in Peril: http://edition.cnn.com/services/opk/planet.peril/for.html
Flow: How did a handful of corporations steal our water:
State of the Planet – The Complete Series .. David Attenborough