I can understand any photographer who manages their own image sales having a problem with copyright infringement because it is clear that there is an infringement.
In the case of Getty their approach is prove you have a licence or pay up, which is fundamentally wrong because Getty acquire a lot of images long after creation or photographers will move their photos over to Getty after creation.
The request is that getty prove they have exclusive rights on the image and haeld them at the time the site was built. If this isn't the case then getty will likely lose.
If somebody can't produce a licence it doesn't make them automatically guilty of copyright infringement. It may be nothing more than poor record keeping where an image was licensed prior to Getty managing its rights which doesn't make anything payable to Getty.
it is the duty of any site owner to make a note of the prevenance of all materials used. I agree most don't, but that doesn't nor should it, lessen the guilt. If the image was pre-getty then fine, no payment due to THEM (there could be a prior rights management agreement in place, or the photographer himself)
It doesn't help that Getty always refuses to provide any documentation until discovery where significant costs will have been incurred.
How can they produce document prior to discovery of the infirngement
by LAW the plaintiff only has to provide such evidence as part of the evidence disclosure, but they DO have to attempt to prevent the matter going to court, and if they have ignored a request for confirmation that they are the sole representative etc, then they seriously weaken their case. Judges do not like having the valuable court time wasted, and if EITHER party is shown to be obstructive in the due process, then it is fronwed upon.