Calling them out and explaining them basic statistics with plain language or simple logic might do the trick.
Sorry to disapoint you, but from my experience, this won't do shit.
The people that follow these "motivational leaders" don't want to hear truth, not even the most obvious ones.
They just want to have the easy sucess. They want to be rich without much effort, and logic doesn't make sense to them.
You can drop all science and logical explanations over their heads and all they will hear is that you are a non-believer and a pessimist, or something alike.
Sorry, but there is no hope there. Most of the people don't want to think for themselves, they want someone to grab their hands and pull them.
That is why it's not so hard to pull a scam like bitconnect.
their is no easy success in life you have to work on it, do your own research about the coins you want to invest then follow it through