It's mostly a matter of perspective. This might help:
As Rodger says, feed 1000 people food full of N&N for an extended period of time, then get an actual result that matches the forecast of over 99% death from stomach cancer, then I will agree that it is a direct cause.
Most of the studies used to support the cancer link are talking about stomach cancer rates of along the lines of "7/1000 people versus 8.4/1000 people". That then makes it into the news as "ZOMG 20% more likely to get stomach cancer!!one1!" So yes, there is a wide body of evidence, but it's not that clear cut; other unhealthy behaviors could easily be responsible for that difference. (As is noted in the studies referenced in your link.)
BTW, you can be assured that all those packages of bacon that say "uncured/no added nitrates/nitrites" are both 1. cured and 2. full of sodium nitrite. The label is allowed because it's coming from celery powder or some other "natural" source. Chemically? No difference. Great for making people feel comfortable while they hand over a few extra dollars, and you still don't have to worry about botulism!
Edit: I shouldn't say "full of sodium nitrate" because these days the nitrate/nitrate content of processed meats is quite low, and also balanced by ascorbic acid or other agents to prevent nitrosamine formation. As I think someone else noted, 90% of your dietary nitrates are coming from your vegetables anyway.