The main--dare I say, the only--weapon in the macro bears' arsenal right now is the flattening yield curve. When the Fed hiked rates yesterday, the five-year Treasury yield rose to a higher level than the 10-year, so that portion of the curve inverted. The spread between two-year and 10-year yields also flattened, to as low as 0.19 points this morning, down from 0.85 points at the start of the year. 

Cue panic that the Fed is making a historic mistake by tightening policy--not just with yesterday's hike, but in their projections showing they expect to tighten six more times this year, once per meeting. The two-year/ten-year yield spread in particular has been a favorite leading indicator of recessions. It has pretty much always inverted before downturns, and rarely inverted otherwise (chart here). And obviously, we're close to it inverting right now.