If it makes you feel any better, I have done worse. When I had a Beemer, I was reversing out of a parallel park at the side of the road. I selected reverse, and my passenger asked what the beeping was. I replied that it was warning me about the car behind, but as I was saying this, I carried on reversing into the car behind. No harm done to either car, but my ego was a little dented. It's fine to turn them on, but you then need to heed their warning.