According to this chart, even though from 2000, FL does NOT even recognize a "good faith and fair dealing exception" to at will employment.
If they did, I would say it may pay to consult an attorney.
http://www.bls.gov/opub/mlr/2001/01/art1full.pdf
It is most probably legal, although such behavior is so egregious, as the Supreme Court says in some rulings, it "shocks the conscience".
I pity the employer who does such to me when my sainted mother dies and I want time off.

