He appears to be using it in a sarcastic manner. He is saying that they are _so stupid_ , that he'll call them geniuses. It's like when someone says:
"Washington DC is the capital of the United States?"
"Yes, you genius!"
You don't mean that they are _actually_ super smart.
In this case,
> and I'll tell you what's more-I think these two geniuses, whoever they are,...
Could be saying the same thing as
> and I'll tell you what's more-I think these two idiots, whoever they are,..."
Disclaimer: I haven't read this book. This is based off of the question alone.