Every exercise that is performed in an unsafe manner is potentially dangerous. It is for this reason that if you are new to exercise you should be taught by a competent instructor.
The kettlebell and in particular the kettlebell swing looks deceivingly easy however there is a specific motion that needs to be done to ensure that the lower back is not taking any unnecessary forces. Loaded lumbar spinal flexion for repetitions is asking for trouble.
Kettlebells are a great strength and conditioning tool and when the exercises are performed correctly they are no more dangerous than any other exercise.
If you are looking for a low impact strength and conditioning workout, check out my video’s on correct technique before attempting these.