No, freezing does NOT kill bacteria. I can't imagine where folks got the idea that it does. Freezing simply puts bacteria into hibernation, and they stop growing and reproducing...well, most bacteria stop. Not all. There is a REASON why you can't keep meat in your freezer forever, and safely eat it. For your home freezer, after 6 months, it's time to throw it away.

http://www.jsonline.com/blogs/news/128887818.html
http://www.newton.dep.anl.gov/askasc.../mole00219.htm
http://www.eatingwell.com/healthy_co...g_foods?page=4

Every time you warm up a rodent, the bacteria in it begin to multiply. Since you can only safely leave raw meat for 3 hours before it's dangerous, that time rapidly adds up. You don't know exactly how long the rodent was out before it was frozen the first time, and if it takes a half hour to thaw, and you leave it with the snake for an hour...then you've used up all your safe time in just 2 attempts.
The rodents we feed have all of their gut contents intact. 60% of feces is comprised of bacteria, by dry weight (hows that for a disturbing fact?) The gut of a dead animal is a virulent mass of bacteria, no longer held in check by digestive enzymes and immune system functions.
While snakes no doubt have more resistance to harmful bacteria than we do, that doesn't mean that the bacteria in dead animals can't possibly make them sick. It's in their best interests for us not to take such chances.