The dangers of topping are many. No foliage means no food, see Botany 101 above. Trees that have stored enough energy to cope with topping grow faster afterward in self-defense, which defeats the purpose of containing growth. Trees that have not stored enough energy die. Sun can damage bark exposed by the removal of foliage.
Cuts are vulnerable to water, insects, bacteria and fungus.
Finally, even if the tree is not killed or diseased, its natural structure is compromised, making it potentially dangerous. We do not top trees. However, he will sometimes make sacrifices to prove his point. Undan tells of a condominium board that wanted several trees topped. One board member stood fast against Undan's objections.