EXCLUSIVE

A former "Grey's Anatomy" stagehand claims producers canned him for bitching about a director of photography treating female employees so bad, they physically broke down.

Timothy Day -- a best boy grip for 10 years -- claims director Herbert Davis made a slew of sexist jokes about female staffers ... referring to them as "idiots" who were not qualified for the job.

Day says it was so bad even Debbie Allen -- who directed several episodes -- complained. The suit claims the harassment -- which allegedly occurred in 2011 -- made some female employees physically sick.

And there's this. Day says he asked the folks at HR whether Davis' comments constituted a hostile work environment, and he claims an HR rep said, "We usually want to hear that he's throwing chairs, screaming at people."

Day says HR told him others complained as well. And he says, he was fired shortly after lodging his formal complaint.