"If Donald Trump doesn't fall, I'll either move out of the country or join the resistance," Diller said Tuesday. "I just think it's a phenomenon of reality television as politics and I think that that is how it started."
Trump responded over the weekend via Twitter, calling Diller "sad and pathetic" on the social media platform.
Front-running Trump provokes strong reactions from foes and supporters alike.
Diller, a media magnate in his own right who currently runs IAC/InterActiveCorp and created Fox Broadcasting among other properties, sees Trump's rise as the triumph of image over substance.
"Reality television, as you all know, is based on conflict," Diller said in remarks at the Bloomberg Markets Most Influential Summit. "All he is is about conflict and it's all about the negative conflict. ... He's a self-promoting huckster who found a vein, a vein of meanness and nastiness."