Frieda: Lightning causes fires and damages electronic equipment.
Frieda's Conclusion
Every building should have a lightning rod.
Frieda's Evidence (since)
Lightning causes fires and damages electronic equipment, and lightning rods can prevent any major damage from lightning.
Erik's Move
It's pointless to install lightning rods because faulty wiring and overloaded circuits cause more fires and equipment damage than lightning does.
Evaluate
Can't we work on all three? If lightning, faulty wiring, and overloaded circuits all lead to damage, let's try to protect ourselves against all three.
If a lightning rod is cheap / easy to install then isn't it still worthwhile for reducing our risk of damage?
You can't say, Doesn't every cut potentially save some money? Isn't that worthwhile? In order for an author to say, , they'd have to establish that we can choose either one to address and can't choose to address both.
Goal
Erik did not convince us that we shouldn't have lightning rods. He argued that other problems are even more important, but he never made it sound like by trying to install a lightning rod, we would undermine our efforts to address faulty wiring and overloaded circuits.
Frieda explained the upside of installing a lightning rod, and Erik never countered that with any downisde.