Sure. Alexa, define grift!
Alexa: Ways of getting money dishonestly that involve tricking someone
While that can be a crime, it is not necessarily. Ponzi schemes fall into this definition easily. However, another good example of this are MLM's (Multi-level marketing) which are totally legal, although they are absolutely dishonest and involve tricking many people, and are basically pyramid schemes. However, they are still legal, although they would certainly classify as a "grift". I need a part of US Federal Law banning the practice of "grifting" or your accusation that I have potentially committed defamation falls flat on its face.