I suspect that you already know this, but keep in mind that Igy's sole focus regarding bonds is purely speculative. That's only natural since he works for Wall Street and makes money from sales. So he naturally focuses on the changing value of bonds on the open market. But holding bonds to maturity will result in a 100% return of principal plus interest, barring default. It's a pretty safe bet though there is always the effect inflation will have on your purchasing power.
I agree with Igy, though for different reasons, that short term bonds may be best. Igy likes them because they generate more sales and thus more money for the company. I like them because in a rising interest rate environment you can more quickly take advantage of higher rates rather than being stuck with lower rates for intermediate or long term notes.