It depends on what you mean by proven. As I said, don't you feel it is much less stressful to have the snake cooled and relaxed, than having to manipulate the animal repeatedly to get your shot? There is plausible information there, Vs. a simple you disagree with that person or this person with nothing informative to back that up.
They're not being cooled to the point of jeopardizing their immune system, or allowing them to get sick. They're not being damaged in any way/shape or form by being cooled. It puts them under less risk of damage by retaliating when they're cooled as well. So what negatively comes of it? They're cooled to those same levels during the breeding season for most species of boids...
As I said before, having your opinion is one thing, but posting it on an open board is another, so be ready for criticism.