"Since non-smokers can get either or both, do you have research showing a high incidence of those diseases among pipe-only smokers?"
I don't have a list of articles in my back pocket, nor do I have a team of scientists at my disposal, if that is what you are asking. I merely stated my pet peeve.
But now that you mention it, I have been reading scientific articles about tobacco smoke and cancer most of my life. Because of my medical background, I can comfortably accept it as fact. You want proof and you are right to demand it, considering there is so much disinformation put out there by big tobacco companies. In my opinion, there is ample peer-reviewed research proving pipe smokers have a higher incidence of mouth, lip, tongue and throat cancers in relation to the general population. These studies have been available to the public for the past thirty years or so. If you think I am misinformed then I would recommend starting with searches of the American Medical Association, National Institutes of Health, Harvard Medical School and Columbia School of Medicine. Don't settle for partisan magazines, blogs, or newspaper articles. Find the original studies then go from there. You seem sharp enough to wade through the technical jargon these articles contain. The internet can help with any terms you are unfamiliar with. Remember, I can't prove it to you or anyone else. You have to do the research and come to your own conclusions just like I did. One or two articles won't do. You need to read at least a dozen peer reviewed studies to get a good start. Unfortunately, some web sources will try to make you pay for the information. Don't do it, and don't fret.
If it's OK with you, I'll PM you this weekend to see what you have so far. If you are having any trouble finding stuff, I'll try to get some good, free articles with the information we need. How does that sound? Do we have a deal?