I already debunked that in another forum, so if you'd be more specific, and quote which figures and time periods you have in mind, I'll work with that too.
But you realise that if everyone would put money in index funds, who would produce, build or create anything? You can't have a nation of investors, someone has to do something with that money. The fact that index funds are making any money is THANKS to people like Trump who DO something.
But he doesn't do much. He's not a manufacturer, he doesn't invent. He's not part of the index (his business isn't nearly large enough). If he invested in other, better businesses, he'd help to finance them to do more than he has been able to do himself.
It's OK that he's not part of the index or not above average, so long as he's not held out to be some sort of business whiz (because he's not).
Also, please link your debunking - I haven't seen it and would like to review it.