You may wish to pm Bbally if you have a specific question about one of his posts. I don't have a problem injecting whole muscle meat because I bring my injection marinade up to temp before loading the syringe. I also think that the cross section of a hypodermic needle is so small, that a very small number of living pathogens are transferred into the muscle meat.
I believe the size of the population of bad germs is important when trying to determine safety standards. During food safety standard development a sample size of pathogens is determined, the test surface is inoculated and the amount of time it takes for the population of bugs to reach an unsafe level is determined at different temperatures. These tests lead to standards for safe food handling. Food scientists need to estimate just how much bad bacteria can be found on fresh cuts of processed meat to determine how long it will take for them to reach an unsafe population if not handled properly
The amount of pathogens transferred into whole muscle meat by a syringe needle is very small. It takes a longer time for those few bacteria to reach an unsafe level. By that time (4 + hours) the internal temps are reached and the small population of pathogens is killed before potentially dangerous residual toxin levels or pathogenic populations are reach
On the other hand, using a syringe to inject marinade into whole muscle meat and then leaving it in the danger zone for an extended period of time without some additional treatment (cure) will allow an unsafe pathogen population to develop.
The best example is using a meat tenderizer that uses scores of needles to cut the tissue. That previously whole muscle must be treated like hamburger because you are transferring a large number of bacteria into the muscle. It will not take very long for a dangerous population of bacteria to develop if not brought to safe temperature rapidly.