The dog can read body language if it is taught what that language means. It can learn that the guy shaking my hands is not being threatening and the guy that is agitated is. I read a post online where this woman said teaching a dog to do this was abusive.
Well there you have it. If some find it offensive that we teach our dogs to recognize threatening situations and behave differently from friendly non-threatening situations they we have to consider where we are as the dog owning public. The lady who wrote that in the post that you read is not fit to own any type of molosser breed.
Please post some of those links where you read this kind of nonsense so I check it out.