Bernanke said that was just one thing he looked at and he's right. The low long term yields don't necessarily indicate low inflation or deflation expectations. Often long term rates fall just because of anticipation of falling short term rates. Anyway, the world is awash in long term money as well as Fannie Mae, GM and other had incentive to borrow short and lend long. That incentive will undoubtedly come back as the Fed caves to political pressures and lowers short term rates. As for deflation, what I see mostly is a huge glut of Chinese and now Vietnamese and other manufacturing undercutting each other.
And in recent weeks he's said that the yield curve doesn't matter. He's reasoning is that absolute rates are historically low. He is speaking as an elitist who thinks he is smarter than the markets. The yield curve is an indicator of how much the Fed is manipulating the market, not absolute rates.
Your reasoning makes more sense. But one should note that the global markets, as they adopt technology and their markets grow, they are going to give us many opportunities to import deflation. The yield curve should not be dismissed on a gut feeling as Greenspan and just about every Fed chairman has done. It is still the best predictor of recession.