He is technically right about Florida requiring brakes if towing over 3000 lbs, but wrong about Florida towing law overriding another state. Reciprocity applies to your driver license and vehicle title & tags, but not laws governing the use of the other state's highways. That would be like saying you can use Florida's speed limits in another state.
Florida does not generally consider a towed car to be a "trailer", so law enforcement typically does not enforce trailering laws for cars under tow. Whether that practice would have any effect on a civil lawsuit that arose from towing the car is another matter, though.
The larger question is the one that John raised - the laws of physics rather than the laws of Florida. an extra unbraked 3000 lbs or so pushing you around increases your stopping distance dramatically, probably 20-50 ft, depending on your speed. Plus you should be obey the chassis towing limits of your coach, i.e. the GCWR (max combined weight of coach & anything towed) and the max weight the coach brakes are designed to handle (the coach GVWR). You really should have auxiliary brakes for most any towed car.