AI will not harm humanity. Nuclear weapons will not harm humanity. Bad humans will.
If someone inside OpenAI had said something like "I predict there is a 70% chance our current corporate culture and leadership will harm or destroy humanity", that would be a much more compelling argument.
It's what you do with the technology that counts.
Because tech people want to build, are paid to build, and "it is difficult to get a man to understand something, when his salary depends on his not understanding it."
I guess any group can become the NRA when their controversial interest comes under scrutiny.