"The probability that a certain person be stupid is independent of any other characteristic of that person."
The stupid person (according to Cipolla's definition) is a threat to the Aryan race in the same way that the stupid person is a threat to all people everywhere, and an Aryan is just as likely to be stupid as anyone else.
It does not contradict it, because you misunderstood my quote.
The Nazi movement, and propaganda in general, succeeds via dehumanizing the enemy, portraying the "other" as "less than human". My use of "Aryan" here was meant to shake you out of that hypnosis, which was created by a a series of arguments which sound logical when viewed in isolation, but have been framed in a restricted narrative chain that leads to the malicious conclusion. It was supposed to wake you up to the fact that once you have accepted the first five tenets unquestionably, you've essentially been brainwashed into the same state of believing the 'other' is less human, and thus measures against this group are acceptable --- which was the defining narrative of the Nazi party regarding the civilised Aryans and their duty against the evil caricatures that seeked to destroy civilisation as we know it.
To use your own words: if you were to believe that a 'stupid person' is a threat to 'people everywhere', you've been brainwashed by this argument into accepting that 'stupid people' are not 'people' (or somehow less than valid people), in the same way that Aryans were led to accept that jews were somehow less human than Aryans, and their exctinction was for the good of the world at large.
And since the term 'stupid person' is extremely vague and malleable towards any political agenda that could stand to benefit from abusing it, this becomes a very dangerous division to make. Not unlike the whole trend of people labelling everyone on the other side as "literally hitler" in modern US political discourse.
"The probability that a certain person be stupid is independent of any other characteristic of that person."
The stupid person (according to Cipolla's definition) is a threat to the Aryan race in the same way that the stupid person is a threat to all people everywhere, and an Aryan is just as likely to be stupid as anyone else.