Mithliyoun or Mithliyeen?
In Arabic, simple masculine plurals take the "-oun" (ون-) or "-een" (ين-) endings. Both mean the same, but are added depending on where they occur in the sentence.
"-oun" is for subjects.
If I want to say, "Gay people are beautiful", I would say "مثليون جنسيا جميلون".
"-een" is for objects.
If I want to say, "I love gay people", I would say "أحبّ مثليين جنسيا".
That's why Helem stands for "Hemaya Lubnaneeya lil-Mithliyeen". It's just grammar. I hope that makes sense.