Is there any legal way to stop sales like that? If it were shown that Equifax were negligent in protecting the data on their systems, could a court demand that they remove all of the data to mitigate further harm?

There are already 3 main credit bureaus who have all of your data. It's not about the data it's about how unethical they are in preventing you from controlling the data.

Think about it: if every person in america put a freeze on their credit, all of these companies would go out of business because they would no longer have a product to sell. It gets even worse if you're a victim of identity theft because they cannot charge victims of identity theft to freeze or un-freeze a credit report.