What is your view on the china study finding that casein (in milk) is linked to a higher risk of cancer?

Rubbish. The "china study" was based on disinformation from the mao-era and post-mao-era chinese government on a gullible team from cornell. They promised a study that would stand up to peer review, but it never appeared. Many people, both children and adults, get sick from milk. If there was a clear link to cancer, real researchers (who are piranhas) would have spotted it already.
Milk and cancer. The study needs to be peer reviewed to see if it was a valid scientific study. When this is established then it needs to be evaluated with the results of other studies.