I don't think that is the argument.

The argument is more "I want to do good thing X, but it will also cause bad thing Y." followed by "Wait, bad thing Y is going to happen anyways, so I might as well do good thing X so we get both X and Y instead of just X."

Viewed this way, the idea is that given the world will have bad thing Y regardless, the one impact of your choice is if good thing X exists or not, and it is better to create good thing X.

Where it becomes an issue is that there is no clear X or Y. There are many different but very related bad things, so if the one you would add is actually better or worse than what is already out there, or maybe it'll exist both ways but you make it more popular, and very subjective things to judge, so different people look at the same outcome and some agree that bad thing Y would have existed anyways and others say that no, this is a new bad thing Z that wouldn't have existed anyways.

>From where I sit it seems reasonable for Anthropic to not want their product used to create malware

Yes, I think there is a PR component to this that is often left out of this discussions.