While I probably agree with your views on religious beliefs, if the goal is to get rid of these kinds of practices, off-handedly insulting people's beliefs prob

While I probably agree with your views on religious beliefs, if the goal is to get rid of these kinds of practices, off-handedly insulting people's beliefs probably won't convince them. It will just put them on the defensive. The best rhetorical approach here is probably to hammer home the fact that, by performing extensive and life-changing cosmetic surgery on a baby, you are violating their rights. This avoids impugning the parents' motives, which they are (for lack of a less abrasive word) aggressively programmed to defend.