You'll be hard pressed to find anything stimulatory/anabolic that does not stimulate already existing cancers. The simplest example, protein consumption can also promote cancer growth (I can find a ref if pressed, I'm just lazy right now).
Given that anabolism can promote tumor growth, do weightlifters tend to have more intense bouts of cancer?
[1] http://cancerres.aacrjournals.org/content/71/13/4484.full
As to the second point the best answer I can give you is maybe. Unfortunately different cancers have completely different mechanisms, while high protein may be bad for mammary cancers it might be good for bone cancers. So it's really situational.
Edit: but seriously, thanks for the response. I think a lot of people are torn by trying to make basic decisions like this, and making sense of conflicting findings is pretty frustrating. Seems like a lot of carbs is bad, though, so I'm going to go with that.
[2] Effects of Varying the Proportion of Protein in the Diet. http://cancerres.aacrjournals.org/content/9/3/162.short
[3]The combined effects of dietary protein and fat on 7,12-dimethylbenz(a)anthracene-induced breast cancer in rats. http://jn.nutrition.org/content/114/7/1213.long