Cecil is (of course) correct to say that microwaves “do not cause chemical reactions”. But chemical reactions, including bond breaking and bond making, do occur in the microwave oven. They are caused not by the microwaves themselves interacting with food, but by the heat that the microwaves generate (unlike the ionizing radiation that Cecil mentions, which directly breaks chemical bonds). These reactions are, as Cecil goes on to say, the same kinds of heat-induced processes that occur in any cooking process.
This is, by the way, the reason why it is extremely unlikely (some would say impossible) that cell phones can cause cancer. The radiation associated with cellphone transmission is too low in energy (too long in wavelength) to break chemical bonds, and, You Tube corn-popping videos to the contrary, not intense enough to cause significant heating of the brain.
Whether “light” is ionizing radiation or not depends on whether you limit the word to the stuff we see. Invisible ultraviolet “light”, especially the short wavelength kind, is indeed ionizing radiation, as anyone who has suffered sunburn can attest. Visible light is not.
None of this is meant to “correct” Cecil (I wouldn’t dare and he got it right anyway), but to clarify the fine points that might lead some readers to foolishly question the Master’s conclusion.