It sounds to me as though you believe that because religious nuts have prophesied doomsday since forever, we can rule out any doomsday scenario as "almost certainly false" (a very confident statement! Prediction is difficult, especially about the future. Weren't you just explaining how hard it is to predict these things?) But no actions on the part of religious doomsayers are going to protect us from a real doomsday-type scenario if the universe throws one at us.

The fact that a claim bears superficial resemblance to one made by wackos might be a reason for you to believe that it's most likely not worth investigating, but as soon as you spend more than a few minutes thinking about a claim, the weight of superficial resemblances is going to be overwhelmed by other data. If I have been talking to someone for three hours, and my major data point for inferring what they are like as a person is what clothes they are wearing, I am doing conversation wrong.

"Nuclear weapons are fundamentally different from every other doomsday scenario I cited because they were designed explicitly and solely as weapons whose purpose was to wreak massive destruction at a huge cost to human life. The potential to destroy humanity defined nuclear weapons. That is not the case for other technological, demographic and resource-related doomsday scenarios, which are much more tenuous."

Sure, and in the same way nuclear bombs were a weaponization of physics research, there will be some way to weaponize AI research.