Citadel CEO Ken Griffin has a blunt message for President Donald Trump: Stop messing with the Federal Reserve. Griffin's warning was relayed in a Wall Street Journal op-ed published on Sunday afternoon. It follows a caustic, summer-long campaign from Trump to press the Fed to lower interest rates. He's railed against the central bank for keeping interest rates steady, arguing it's put a fence on economic growth. The Citadel chief executive said Trump's efforts threaten to severely backfire on him, causin ...