:)
I remember when this article first appeared. And like you, I drew the same initial conclusion ("Vitamin D can cause cancer in smokers and ex-smokers").
But read it more closely:
New research appearing online today in Clinical Chemistry, the journal of AACC, shows that decreased levels of vitamin D may predispose smokers to developing tobacco-related cancer.
Everything I've read indicates a proper level of Vitamin D in our body is necessary to prevent all sorts of ailments, including the prevention of cancers.
The article could have been written more clearly. Saving the link for future reference. Thanks for finding and posting it. It mislead me too, at the time.