Seeing a synchronised murder squad butcher their way through an 18th Century Parisian ballroom was my first 'wow' moment of E3. I watched Microsoft's press conference huddled around a TV in our office with staff from various magazines and web sites, and as the hooded assassins continued cutting a swathe through French noblemen, a female colleague from our video department noted that at least she'd be able to play as a woman in the co-op mode. Another colleague made the point that it still meant playable female characters were being segregated outside the main mode, or only allowed to star on niche formats like PSP. It turns out they were both being too optimistic.

Ubisoft's explanation for the fact that, sorry, you actually can't play as a female in Assassin's Creed Unity's co-op mode is so startling that it bears repeating in full: “It was on our feature list until not too long ago, but it's a question of focus and production. So we wanted to make sure we had the best experience for the character. A female character means that you have to redo a lot of animation, a lot of costumes. It would have doubled the work on those things,” technical director James Therien told Videogamer . He added: “And I mean it's something the team really wanted, but we had to make a decision. It's unfortunate, but it's a reality of game development.”

A reality of game development. How depressing is that? Put aside, for a second, the fact that this is a blockbuster costing 10s of millions of dollars, which as Brenna Hillier at VG247 notes has no less than nine separate studios working on it. Put aside, even, the fact that previous Assassin's Creed games have had playable women as part of the multiplayer component, or that Brotherhood had you supported by on-call assassins, many of whom were female, so it's hardly like it can't be done. Ignore all those things and just focus on how disastrous it sounds to have a senior figure for one of the most supposedly progressive developers in the world describe the option to play as women (of whom, last time I checked , still represented half of all humanity) as being an unnecessary drain on resources.

The miserable sense here is of femininity as an optional extra. Something on a long list of features that might be nice to have, but that like a set of side missions can be cut if they prove a pain to implement. Silly girls with their harder to animate hair! Surely this isn't good enough. And from the squirminess of his answer, I suspect Therien knows it. That he references how much the team wanted to include playable female characters suggests to me that this is probably a decision which hasn't gone down well internally.

I've been to Ubisoft Montreal several times, and it has always seemed like a studio which prided itself on its diversity. It's also worth noting that, (perhaps just as a defence mechanism, given the original game's Jerusalem setting), Assassin's Creed always begins with a boilerplate message stating: ''This game was made by a multicultural team of various faiths and beliefs.” It's starting to feel like that caveat also ought to include “hey, and some girls!”

My interest here is not in trying to whip up some tedious Twitterstorm. However much you want to roll your eyes and call it a manufactured controversy, this stuff matters. It feels like we're at key moment in the evolution of games in terms of the kind of protagonists we're going to be expected to play. Nor am I trying to paint Ubisoft as pantomime villains, blundering around gender and diversity issues while everyone else is getting it right. Almost no-one is getting it right.

Take the recently-announced-for-PC Grand Theft Auto V . When asked why none of the three leads could have been female, Dan Houser told The Guardian that: "The concept of being masculine was so key to this story." I just don't think that washes. It'd be easy enough to imagine playing as a Carmella Soprano-style character, dragged into the family business, or maybe as a corrupt female cop. The simple answer is that Rockstar didn't want to. Just as Ubisoft don't want to. Like almost no AAA developer wants to.

Of the developers taking this stuff seriously, Bioware is probably the gold standard. And even then it took them three Mass Effects before Fem Shep started to be used in the marketing material. For Dragon Age: Inquisition's box art the issue has been cleverly dodged by having the lead character wear so much armour you'd need an ultrasound to find out what's underneath. To be fair, Bioware also took the trouble to use male and female protagonists in different trailers at E3 this year. They're taking leadership here.

I think the uncomfortable truth is not that other mainstream developers hate women, or racial minorities, but that there's a deep-seated assumption that the core audience for these sorts of games is mainly white men and boys who won't accept anything else when it comes to who's presented as the public face of big franchises.

I also believe that many developers at big studios want to start changing that assumption, but struggle to do so in the face of the perceived risk. Earlier this year, Tom called the speech given by Bioware's Manveer Heir about stereotypes in gaming the most important moment of GDC . Last year, Assassin's Creed IV's 'Cry Freedom' DLC cast you as Adéwalé, a freed slave whose storyline centred around confronting the brutalities of slavery. But while 12 Years A Slave was winning an Oscar for Steve McQueen, here the same themes were only touched on in the main game and then hived off as downloadable content. It's like Ubisoft knows what it wants to do, but is struggling getting there.

We've all got a long way to go. But the only way to start is by talking about it, and to talk about it without all the usual kneejerk defence mechanisms. Yes it matters. No it isn't political correctness gone mad. We can all do better. As an editorial team PC Gamer is almost entirely white, male and middle class. We can and should aspire to offer a greater variety of voices. As I started writing this I could hear my colleague from the video studio talking to the rest of her team about how she was wrong about the playable characters in Assassin's Creed Unity, and about how frustrating it feels for her. She was making jokes about it, because she's funny, but she also sounded furious. She has every right to be.