1. Inflation remains subdued, well below the Fed's 2% target, as exemplified in the Fed's favorite inflation indicator: Core PCE (personal consumption expenditures), which is up just 1.3% year over year. In addition, U.S. headline inflation is currently lower than inflation in the European Union, which has negative interest rates, and the U.K.

2. U.S. economic growth, adjusted for inflation, is only slightly stronger than European growth: Two percent year over year versus 1.5% while ECB President Mario Draghi is considering more economic stimulus. “Why is doubling down on stimulus appropriate in Europe while with similar GDP the U.S. is thinking about raising rates?” Gundlach asked.

3. Fed governors are split about making the move.

4. Interest rates are already rising gradually across the yield curve. The only rate that hasn't risen is the federal funds rate, Gundlach said.

5. The junk bond index, a “great leading indicator of financial conditions,” is at a four-year low.

6. The Goldman Sachs Financial Conditions Index, which rises as conditions worsen, is much higher than it was in 2012. “Why raise interest rates now?” asked Gundlach.

Once the Fed does start raising rates, the world changes, said Gundlach. He pooh-poohed sentiment that a 25 basis point (0.25%) Fed rate hike is no big deal.

“About two-thirds of today's money managers have never experienced a single Fed rate hike,” Gundlach said. “How do they know what will happen?”