Not one to waste time, Keyes jumps straight to the bottom line: humanity is doomed and will end in a few months. The cause? Deadly microwave radiation will cook us since we'll no longer be shielded by the Earth's magnetic force field or what Keyes refers to as "Earth's electro-magnetic energy field".
Keyes proceeds to demonstrate the effects of losing the magnetic field by lighting the aerosol from a can of hair spray and flaming a peach representing Earth. He makes his explanation simplistic since he's talking to military brass who can't grasp complexity, even though they lead one of the most complex and high tech organizations in the world.
Not only does Keyes not know the difference between forces and energy but he apparently believes that electromagnetic radiation such as microwaves can be deflected by a magnetic field. Here's a quick experiment, try using a magnet to deflect the electromagnetic (EM) radiation emitted by a flashlight. The EM radiation is a beam of visible light and, although we hate to spoil the experiment, nothing will happen.
Whether Earth did or didn't have a magnetic field would make no difference as far as microwave radiation is concerned. First, the magnetic field doesn't affect it, and second, there's very little of it in the first place. The Sun emits lots of electromagnetic radiation but most of it is visible light. It sends very little microwave radiation. At its worst, the Sun's microwave radiation can cause interference with radio or cellphone transmissions but poses no significant health hazard.
The Sun does periodically emit potentially dangerous quantities of plasma during solar flares. It's made up mostly of protons and electrons with high amounts of kinetic energy which can, indeed, be deflected by magnetic fields. The Earth's magnetic field does give some added protection from the solar wind. However, even without the magnetic field the atmosphere would still effectively shield us.
There is little reason to panic over a magnetic field upset. The geological record indicates Earth's magnetic field reverses itself at irregular intervals averaging about every half a million years. While the magnetic field probably doesn't drop to zero during these times, available evidence suggests it becomes weak and erratic. Undoubtedly, some bad things happen but there's no evidence that such fluctuations cause mass extinctions, let alone incineration by deadly microwave radiation.