>Everything that you're saying can be done with open-weights models by bad people can also be done with closed-weights models by the people who own them.

The latter is a much smaller group of people located in a limited number of countries. It's clearly easier to keep a limited number of entities in check than a wider group that might include 100s of thousands to millions of entities.

>And there is no defence against that, we are forced to trust that the owners are not bad people.

Yes there is; Regulation and oversight. As all developed nations do with technologies that present a risk to public safety.

>At least with open weights we know the danger

We would have a better understanding of the threat in some ways, but worse in others. Having access to open weights models gives us no insight into how and where the models are being modified, deployed, and used elsewhere.