I certainly agree with you that cancer is not caused by emotions, though I think that emotional issues can contribute to one's susceptibility to cancer as well as retard recovery.
I am not so sure about viruses being the cause of the "vast majority of cancers", unless the viruses are either new ones or else they cause cancer in combination with other factors. If viruses alone are the cause, wouldn't that mean that the viruses that cause cancer are pretty much a modern development since the proliferation of cancer is very much a modern phenomena?
Obviously diet, nutrition and lifestyles which lead to impaired immune systems and impaired livers are factors. What role do you see the increased exposure to manmade toxins playing? Incidence of cancer and other diseases and industrialization/chemical exposure closely parallel.