This has been linked to a few times now. Here's my response from another thread (adapted):
Correlation does not imply causation. First, many of the store-bought processed meats contain less than ideal fillers. Check the label. Second, they didn't take into account the rest of the diet of those in both groups. People who eat a large amount of processed meats are also more likely to eat other things that are questionable for their health, i.e. processed grains, sugars, etc. which I'm assuming are the real culprits.