The best way to make such an argument is to focus on the idea that courts are needed to enforce common sense ideas of consumer protection. Without courts, there would be no good way to protect consumers.
You could argue that the market would protect consumers. It would prevent firms from harming their customers and force them to compensate those who were harmed. It would do this because other consumers would not patronize businesses that abused consumers.
However, consumers typically do not have the kinds of information and resources that would be needed to police businesses in this way. The average consumer would not be able to monitor a business's practices to know if that business was likely to harm them. Laws and courts are needed, therefore, to protect consumers who would not be able to monitor businesses and police them on their own.