If you saw "Infected," the group learned that sharing the water, which was also used for the pigs, caused the fluids to be exchanged and led to a virus like infection which caused one of the boys in the prison to become ill and turn. It was the first time the group realized that this is how it was also being passed. The pigs were killed because they drank from the infected water and couldn't be eaten safely. So, eating someone that has been bitten, yes, you can turn. Now if Bob had said something, maybe they could have chopped off the leg like they did for Hershel - who had the same thing happen, but he survived by having the infection cut off....but Bob said nothing. I suspect he was crying at the end because he was planning to shoot himself but he was attacked by the Terminus group.