It's not the nitrates themselves, it's the derivative nitrosamines that are more implicated in GI cancers. And I'm not sure why you mention blood pressure, since that really doesn't have any correlation that I know of with GI tumorigenesis.
Yeah, my post was too short. What I linked to talks about how the evidence about cancer isn't as damning as originally thought and how there are health benefits to nitrites that are the result of dietary nitrate. And you are correct about nitrosamines. Stephan goes over that.
Anyway I'm against creating a boogeyman with animal products when it's probably a dead end. Not useful advice. Really people should avoid junk food, packaged food, fast food, etc. At least for people that cannot seem to control appetite. I mean just look at the food porn going on in this thread right now. I don't think normal food causes this sort of infatuation.