Wanting Horo instead of Holo, is like prefering Luffy's name to be Ruffy, japanese people are bad at saying L's, my japanese teacher has been living in my country for a while now and she told us that it was very difficult for her to get used to the L sound, since that's a sound they don't originally have.
My name for example, my Japanese friends call me Pauro, but my name doesn't have an R, it has an L.
In some cases it's hard to figure out which name is right or wrong, however once there's an official clarification, I see no point to keep insisting on the wrong one. =O