I don't think that defensive substances to made the plant unpalatable should be put in the same category as modern pesticides, designed to kill everything by contact (including predators) instead of to deter the plant eaters. Is a totally new level.
This is not an accurate statement, obviously modern pesticides are not as targeted as would be optimal but they are most certainly not designed to kill everything by contact. For example I will apply Coragen later in the season when I need Grasshopper control, despite greater expense, because it is much less harmful to bees than more cost-effective options.