Is using antibiotics in livestock and poultry problematic? Critics say that this practice is contributing to antibiotic resistance, with potential risks to human health. Defenders say the risk to humans is exaggerated and that the benefits outweigh the risks. Surely this disagreement can be sorted out in a straightforward fashion: just collect the scientific evidence and make a judgment. But, unfortunately, things are not this easy. Here I present a number of generalizations about scientific controversies, based on previous research. For each generalization, I give a few examples from other controversies - especially those, such as fluoridation, that I have studied in depth - and then offer an assessment of its relevance to the controversy about antibiotics in livestock and poultry.