If that was the distinction to be made, using ChatGPT as a classifier would be acceptable while using it to write new spam (see the "I am sorry" amazon listings of the other day) would be unacceptable.

If two different uses of a tool allow for both infringing and non-infringing uses (are photocopiers allowed to make copies(!) of copyrighted works?) it has generally been the case that the tool is allowed and the person with agency to either use the copyrighted work in an infringing or a non-infringing way is the one to come under scrutiny.

I believe that if it is found that OpenAI is found to have committed copyright infringement in training the model, then an argument that training a model on spam be considered to be copyright infringement could be reasonably constructed.

If, on the other hand, OpenAI is found to have sufficiently transformative in its creation of the model and some uses are infringing, then it is the person who did the infringing (as with a photocopier or a printer printing off a copy of a comic from the web) that should be have legal consequences.

The extent to which it supplants the original work is one of the fair use considerations.

I think it'd make more sense to have a stance of "current LLMs and image generators should be judged by fair use factors and I believe they'd fail", though I'd still disagree, instead of having machine learning models subject to a different set of rules than humans and traditional algorithms.