It doesn't matter what any of us think is actually dangerous or not. The FAA regs prohibit the use of any transmitting device onboard the aircraft in flight. It's much easier for them to write the reg that way than to codify all the good devices vs bad devices. And there are definitely some bad ones out there that fall under that regulation. I don't remember where I saw it, but I do recall a test of some common household RF devices. RF operated toys (cars, trucks, etc) were really bad, causing all sorts of interference with nav equipment.

joe