Sorry, but I'm guessing you don't spend much time around religious conservatives like Robertson. It's actually quite common among them to reason philosophically like this, mainly due to the emphasis on Christian apologetics. I'm sure Robertson has come across an argument of this form before and just reworked it for this.
Let me offer some more evidence. Listening to a recording of it, there are some chuckles in the audience at the beginning, but it grows silent by the end as most people grow more disgusted. The natural reaction, right in his last line, is, "Yes, something isn't right about this. Atheists do not deserve to be raped, murdered and castrated. The world would be quite chilling if we didn't have the moral authority to declare that some things are right and some things are wrong."
That's the complete opposite conclusion as, "Yes, atheists deserve to be tortured for believing there's no right and wrong." I honestly don't see how you think that could be the conclusion he wants you to reach. You don't promote the Holocaust by talking about how much pain the Jews would suffer in concentration camps. You use weasel words like "the final solution to the Jewish problem." Robertson is doing the exact opposite.
The fantasy isn't mainly that Robertson likes torturing atheists or thinks his audience does. The fantasy is that their own atheism is responsible for them being tortured and that the awfulness of that demonstrates that atheism is awful. Whether his audience likes hearing about atheists suffering is a side issue.
.You don't promote the Holocaust by talking about how much pain the Jews would suffer in concentration camps.
That's a bad comparison because Nazis did not believe that Jews could or should give up being Jews.
Link to Blog Post: "Extremism in Thought Experiments is No Vice"
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