When I worked as a valet at a LV hotel/casino the insurance companies required that we back in all cars because it is safer and decreases the chance of an accident.
If you are loading groceries, fine. All other times, it is better to back in first.
The people who hate those who back in are the same who deny zipper merging is superior and camp in the left lane because they are going the speed limit and nobody needs to go faster than them. Bad drivers and bad people.