I don't have a spider but I'm well aware of the wobbling gene some may have. But that would have not stopped me if I wanted one badly. It is similar to the idea of should one continue to support the breeding of certain dog breeds, like the English bulldog? They can barely breathe, they can't give birth naturally and have other genetic issues.
To answer your question, your support of whatever it is in demand, like the English bulldog, will make not matter in the grand scheme of things. If you don't buy one, someone else will. If you do get one, you are giving a good home to that pet. Which do you prefer? Some people should not breed but they will continue. So what you can do about it is to pick a reputable breeder who tries not to breed the wobble gene if it is such a concern to you.