After studying a Lenny, we got these results Lenny's appear to have a unique genetic trait that, when causing others aggression or being overtly sexual, release massive amounts of dopamine. The concept of a weapon is ridiculously simple: repress the gene, and the lennys become docile, due to a lack of gained dopamine. Armor to prevent Lenny's could be made up of a reflective material, causing the lennys to feel their own trolling and die out.