Which is exactly why we can produce so much food / acre. Land use would need to go up significantly, and thus the price of food, in order to be able to use "natural" methods of pest control. This would affect developing countries the most.
For all of our medicines, we or our doctors have to make a judgment about whether the side effects are worth it for the therapeutic value that we get. If we said that we would never deliberately use any poisonous substances, we might have to throw away most of our pharmacopoeia.
You can try to make an argument against pesticides on the basis that their side effects aren't worth it (and I prefer organics myself), but I think the fact that pesticides are "poison" doesn't get you there by itself.