Lactose intolerance is actually normal. It’s tolerance to lactose as an adult that is biologically unusual, and mostly unique to westerners. Because most of us continue eating dairy products after infancy, we continue being able to digest them. However other cultures don’t continue consuming dairy after infancy, and thus lose their ability to digest it effectively.

It’s a really tough argument to claim it as a disability. I don’t see this case going well for the plaintiffs.