Yes, some people should never have dogs...and certainly not have pups from them.
Even though the lurcher has attacked other dogs and such, her maternal instincts will stop her attacking her own offspring. She probably has some reason as to why she attacked the other dogs such as feeling threatened but this reason won't apply to her own pups. It's still very wrong to have them shut up in a little shed all the time though. New welfare laws will mean that this treatment is now illegal and all pets are required to be provided with all basic needs, including exercise, by law so be sure to let us know what the RSPCA say about it or anyone else for that matter.