I have a difficult time understanding why people think that going from a balmy 85 degree environment directly into a sub 30 degree environment is the "same as hibernation".
In the wild any animal that hibernates has a chance to begin to adjust to the changing temperatures through the natural change in seasons. It doesn't happen at the flick of a switch. Their bodies receive information from the varying temperatures and day cycles that tells them to begin preparing to get cold. All sorts of biological processes are switched on (or off as the case may be) during this transition.
Yes, cooling a reptile down will also slow them down and eventually cause them to "sleep". At THIS point they would most likely be in enough of a stupor that they would not notice the cold or pain. However, going directly from a very warm environment to a very cold one will ALWAYS result in discomfort.
The animals you are throwing into the freezer without proper preparation are not dying from the cold so much as they are dying from the SHOCK. Death by shock is a very traumatic thing for any species.
Whether the animal is ectothermic or endothermic has very little to do with how they will "feel" when going from one temperature extreme to another. Either way it will be a shock to the system. Beyond that a reptile will have much less ability to adjust to the temperature change and will most likely die from shock before any of it's tissues actually freeze. Endothermic animals (mammals, ect) would take longer to die in this type of environment, but their bodies would go through all types of phases that would allow them to slip into death in a more comfortable manner.
Ever been taking a shower and have someone run the hot water somewhere else in the house? Your hot shower is suddenly ice cold... imagine if it was ice and you couldn't escape.
Bring it to the vet... despite what so many people say vets aren't the morons you might think.... of course I'm a vet student so I'm a little biased.