I'm absolutely certain Linux has been used to kill children. Detergent, pesticide, and even pillows too!
Tools shouldn't be limited based on what the worst way they can be used. Stable diffusion is an absolute positive for society. Even when it's used to generate CP, every image that model creates is not one that involves a real kid.
The cat is out of the bag when OpenAI announced DALLE. Stable Diffusion only accelerated it a bit. Even if Sablity or lawmakers manage to prevent or outlaw open models, criminals will continue to build their own and ignore laws.
The only thing their reluctance does is harm Stability and give their competition a chance to catch up. Perhaps that's a good thing. Maybe it's time for another organization to take the lead.