As someone who’s never had a kidney stone, that seems like strange advice to me. Is there some kind of research behind it that you’re aware of, or is this some kind of folk medicine assumption that the calcium in dairy will lead to stones?
I did a quick google search, and my first return from the National Kidney and Urologic Diseases Information Clearinghouse (sponsored by the U.S. Department of Health and Human Services), stated that dietary calcium is not a concern in stone formation, and in fact may be protective:
“Calcium from food does not increase the risk of calcium oxalate stones. Calcium in the digestive tract binds to oxalate from food and keeps it from entering the blood, and then the urinary tract, where it can form stones. People who form calcium oxalate stones should include 800 mg of calcium in their diet every day, not only for kidney stone prevention but also to maintain bone density.” (http://kidney.niddk.nih.gov/Kudiseases/pubs/kidneystonediet/index.aspx#calcium)
In short, you should drink as much milk as you want. It might even help prevent future stones, because it will keep oxalate out of your urinary tract.