Ret-conning sexuality. Is it ok to change this kind of thing after the fact?

I just finished the Varus lore. I was disappointed. The story was fine, although it seems to jump forward a bit to much between pages. The issue I have is with the decision to alter his sexual preference. I am happy that Riot wants to represent all walks of life in the game, ex. race, religion, sexual preference, body type ext. I think it is healthy for the game and community. However, changing something so core to who a character is ruins them for a lot of long time fans. Imagine if they made Tony Stark gay or black or a woman in the new Avengers movie. Don't you think people would have a problem with the change. Its not the fact that the change is bad per-say, but it is no longer the character we expect them to be. If Riot wants to diversify the character lineup as far as representation goes, it should do so at the beginning. It shouldn't make changes so core to who a character is. I support all walks of life, its a good idea to add diversity, but very poor execution of Riots part here.