He does what a lot of people do, they take a little bit of information and spin it whatever way they can to make themselves feel better and/or to appear superior. One can not win an argument with these types of people since they refuse to use logic and are fueled by hatred or some other negative facet of their pathetic personality. In the past, I have debated various topics with scientific evidence (I'm a scientist/biochemistry field), and people like him, it does no good.
For example, his comment about nicotine being used as a pesticide... Would it matter if I told him that yes, it is true, but only for organic farming because it is derived from a botanical source? No, it would not matter, he's set in his close minded ways.
Or would it matter if I explained that nicotine is being used in several clinical trials for memory disorders like Alzheimers and MCI because in people who are suffering with these diseases, their level of acetylcholine in their bodies may be altered, and since nicotine imitates acetylcholine, it helps with memory loss... And would it matter if I explained that nicotine stimulates receptors on neurons involved in learning and memory, called cholinergic neurons? Nope, it would not matter to him. His thinking lacks logic, he's driven by his emotions.
Best just to walk away from people like that. Waste of time, but that's just my thinking.