F/t prey can easily damage or even kill a snake if fed improperly. If the prey item isn't thoroughly thawed, it will rot in the snake's digestive tract causing a regurgitation or possibly death if the snake is unable to regurge.

The limbs and nails on f/t rodents are generally harder/less pliable because of the onset of rigor mortis, and may scrape the inside of the snake's mouth or esophagus, causing an infection which can lead to an abscess. If the infection is left long enough, the bacteria can lead to sepsis, which is a guaranteed death without massive amounts of strong antibiotics.

Your snake has evolved over millions of years to be very efficient at hunting and killing prey. I've seen my snakes take a bad grab every so often, and even if the mouse is able to bite, the snake knows that and will wrap tighter or wrap another coil around to immobilize that mouse. Their epidermis is tougher than you think, snakes aren't delicate little flowers with paper-thin skin. Rodent nails aren't going to leave huge gaping wounds in their skin and minor bites aren't going to affect them as long as they have a decent immune system.

SO! Feed appropriate sized prey items(adult mice or nothing larger than a small rat-55-65g in weight) and the snake won't have any trouble. Feed large and jumbo rats and that's where you get into problems. Pre-scenting the room prior to feeding is also a very important aspect in feeding live or f/t.