Title needs changing to "gay harem" or something. Harem by definition means women with men.
Yes, it was brought up before. No, it doesn't need to change.
Harem by its original definition is a muslim custom, as you yourself brought it to our attention. Now it's used by japanese anime.
Should all the anime also change the word they use just because it doesn't fit exactly into its meaning?
Also, the meaning of a word changes when it's brought out of its origin culture.
What people use it as currently is more important than what its written meaning.
Such is how language works. It's easier to change what some outdated word used to mean than to change people's definition of it.