EMP, MRI, or what about anti-nanobots? If you can program nanobots that kill people with particular DNA, couldn’t you program nanobots that target other nanobots? I would assume they hadn’t yet built in a self-defense protocol for the nanobots since they were cutting edge and not assumed to have any countermeasures yet. Anti-nanobots seem just as plausible as DNA targeting nanobots.
Taking someone’s lead sounds like a British saying indicating the opposite of following someone’s lead. It sounds like you’re taking someone’s leash in your hands and directing them where to go.