No, I do not agree with this statement. I think that anyone who wants a ball python is going to get one regardless of how the bacteria in their mouth is classified. The general public either does not have the knowledge base or simply doesn't care about if the bacteria in an animal's mouth is good or bad (as pointed out by the multitude of bacteria in cats' mouths.) HSUS and others would care very much about a study and you can bet such a study would be included in their talking points to ban exotic animals, of course with the designation of harmless conveniently left out. So, such a study would be helpful but to those trying to ban exotics.
There's also nothing wrong with someone refusing to let you swab their animals. It doesn't make them narrow minded or exhibit ignorance of what you are trying to do. I have a degree in Biology, as well as several published papers, and would never let anyone experiment with my personal collection, even just collecting saliva samples.