All electromagnetic radiation is formed of a continually oscillating electric field vector (oscillating between +Amplitude and -Amplitude) with a magnetic field vector doing the same thing, but perpendicular to it.
Microwaves (and radio) are produced by oscillating electric charges. When the charges are moving one way it's a +ve current and -ve if the other way. Microwaves are microwaves, there only differences are the power and frequency.
In terms of what this guy's saying, microwaves only heat up food because they make polar molecules (like water) vibrate. They don't do anything to the internal workings of the molecule (unless it gets hot enough to break up).
Simply put, microwaves don't have enough energy to cause 'chemical' changes in atoms. This is how UV, XRay and Gamma causes cancer, by altering the chemistry of DNA molecules in your cells. There's no way microwaves can do that. It's possible that there may be another, more complicated mechanism that could be activated by them, but I doubt it.