I actually find mmcsky's comments about the psychology of this rather fascinating, as it's an aspect of it all I hadn't really given much consideration. While I doubt a post on page 15 of a thread on an MMO forum is going to sway anyone, it's worth reflecting on how many demands of rights are made on behalf of a virtual avatar.
I've seen a lot of posts on how there should be equality for all players in regards to romantic events or the upcoming marriage system. Why is that? I mean, what is the real reason people want their virtual avatars to be able to do this thing? Although there are like as not to be many answers, one I've seen continually used in reference to these situations is how these games are escapism. In essence, people do not want to be reminded of what they face in real-world situations within a medium they've chosen to help distract them from those issues. Moreover, it's plausible that the apparent high volume of their protests against these situations is due in part a sense of empowerment the medium lends itself; I'd perhaps even go so far as to say this is because of a lack of empowerment many individuals feel in facing these issues in real-life.
The nature of the MMO medium has evolved in such a way as to allow people more personal investment in their virtual avatars. I mean, let's even consider that word, "avatar". In an MMO such as this, you don't play a character in a traditional sense, one that was created by an author with a pre-defined persona. Players are the creators, and the avatars we create are our own expressions of a hero, defined within the context of the game's toolset. Therefore, to some extent, there is a sense of ownership of that avatar. "It is my character." This isn't the case in a traditional MMO, where you're limited to perhaps choosing a name for the protagonist, but that truly is the limit of a player's involvement; the rest is just playing out the story that someone else wrote. In an MMO, though, players "write" much more of the story, if you will. Appearance, jobs, crafts, progression choices, on and on: a player creates their own journey through the game world.
Given that context, I think I understand people's desire to advocate for more real-life representations to be extant in the game. That being said, while I think I'm beginning to understand it, I don't believe I agree with it unequivocally. As I've said previously, a game needs to hold to some kind of creative vision. That creative vision encompasses a certain scope to the game, and it strikes me that this is where the conflicts are arising. SE clearly had a creative vision in mind for this event, to mimic two real-life holidays, and give players an opportunity to have a "fun" little side-quest to perform. Yet, by injecting their creative vision into an area where players feel they have control (i.e. their player's sexuality), we've now encountered a conflict of interest. People here have decided that the sexuality they've chosen for their character, a choice very worth noting that is only ephemeral in nature and not coded into the game, has been discriminated against, and by extension, they have been discriminated against.
This is where I feel it's important to step back and look at the scope of the creative vision. There is no sexuality choice in the game. SE could have easily created that as a factor of their character development toolkit, and they chose not to do so. That's really important to understand here because it means, at a very basic level, it is not a priority for SE's vision in this game. To put it another way, your avatar's sexuality doesn't matter to them or what they're trying to sell you. Given that, expecting them to cater to your character's sexuality is probably misguided, at best.
Based on those things, it might be worth reconsidering how much of your own sexual identity you project into the game. It seems highly like SE will continue to disappoint expectations in that area because it's just a non-issue for them. Frankly, given how much of a non-issue they've tried to make it, it'd probably be smarter on their part to scrap the upcoming marriage system altogether. Sexual identity is clearly not a priority for them, and they don't appear to the have the wherewithal or resources to make it one.
tl;dr: SE didn't make a real-life simulator, so it might be a good idea to invest less of your own identity into the game.