I've never caused any damage using magic loop. I find it the easiest method of knitting small things in the round, though I use 40cm circulars for hat knitting.
Longer cables do make it easier and if I feel like I'm getting flustered due to a lapse of concentration or I'm finding the cable a bit twisty, I arrange both halves on the needles, tips pointing right, and rearrange everything as necessary (my wits, included) before pulling the needle through from the back and knitting onto it. I find that everything falls into rhythm quite quickly after doing that a few times.