Let me put it this way: it's not great to live in a world where the immense majority of nukes are controlled by Donald Trump and Vladimir Putin.
But it's arguably better than living in a world where every single citizen has a nuke.
(Though the potential for harm of diffusion models is far below nuke; it's not "kill millions of people", it's "produce cheap disinformation and very convincing fake evidence to ruin someone's life")
I think that would be a tough argument to make (in regards to image generation). The same could be said of just about any computing technology. The problem is we lose out on a lot of potential good.
Either way it doesn't matter, you can't control bits like you can enriched uranium. It's just a matter of time. In the grand scheme of things Open AI will be irrelevant.