For clarification and in Tesla's defense: If I've correctly read some of the descriptions of his idea, it didn't involve "energy from nothing" and hence no obvious violation of thermodynamics. Rather, it involved (roughly) building huge antennas/lightning rods to tap into the natural electric potential (against ground) of the ionosphere.
As I understand it, the idea is simply impractical. But there's a huge Tesla fan base among the intersection of conspiracy theorists and amateur (pseudo)scientists who believe that Tesla's idea was scuttled and suppressed by Big Electric to protect their monopoly on generating electricity in harder ways.
I can't fathom why anybody in their right mind would choose to call their scheme "free energy", e.g. choose to associate themselves with perpetual motion nuts. We can get electrical energy from sunlight, which is pretty damn neat, and nobody calls that "free energy."
As I understand it, the idea is simply impractical. But there's a huge Tesla fan base among the intersection of conspiracy theorists and amateur (pseudo)scientists who believe that Tesla's idea was scuttled and suppressed by Big Electric to protect their monopoly on generating electricity in harder ways.