The idea that only intent matters is a pretty shallow and widely discredited way of thinking, to be frank.

But my point wasn't JUST that to this person what the content creators intent was is irrelevant, but also that to said person their interpretation was to be held as more valid than the original creators, even when the creator pointed out that it was fundamentally misplaced.

Intent isn't everything. But if the authors intent is nothing, so is any interpretation of the authors intent as "transphobic" etc. You can't have your cake and eat it, since the two are fundamentally linked. Discounting one discounts both. Unless you can explain why interpreting an authors intent is fine, even if the actual stated intent is a poor way of looking at things?

Outrage is legitimate if it's rooted in a (proportionally important) moral principle, as opposed to something petty like one's selfish desires or bruised ego. Outrage over bigotry is legitimate, outrage in defense of one's bigotry isn't. Of course, people will disagree over the moral principles in play over any controversial issue, and that's fine.

I disagree entirely on many points, this bit will be long [you've been warned.] Lets start:

Proportionally important moral principle

Define this. I would not say outrage at an ambiguous joke in a video-game that is proportional, especially not when very real and tangible transphobia exists and is frequently ignored.

Secondly, explain to me why you think X moral principle should be applied objectively. You have no right to supersede someones own morality with your own, lest the same happen to you. You are not a moral arbiter, neither am I, neither of us have any fundamental right to claim our moral code is THE moral code, ergo appealing to morality is fundamentally misplaced as it is an entirely subjective appeal.

as opposed to something petty like one's selfish desires or bruised ego

Some peoples morality [such as philosophical satanism] is centred on the self. That doesn't make it inherently less valuable, it's just a different kind of moral philosophy. Again, you aren't a moral arbiter, you have no right to try and judge different moralities as inferior or superior to your own.

Outrage over bigotry is legitimate, outrage in defense of one's bigotry isn't

That is a double standard. Plain and clear as day. Allow me to explain why outrage isn't legitimate, period.

I'm part of the LGBT community as a gay person. By your logic, if I encounter a homophobic person, I can simply say "I don't have to listen to your argument! It is offensive, and I am justified in that offense! Being homophobic is wrong!"

The homophobic person can reply "I don't have to listen to your argument either! It is offensive, and I am justified in that offense! Being Gay is wrong!"

It's not fine if a homophobic person says it, because they are pushing their moral convictions as facts and imperatives. Guess what? It's still not fine if a gay person like me says it, because I'd still be pushing my moral convictions as facts and imperatives.

When I want to argue against a homophobe, I don't use their logic, because I've already rejected their logic. I rely on principles - such as, we're all human. Let's just live and let live. My life is none of your business, your life is none of mine, we don't have to interact if it makes you feel uncomfortable, but if you ever want to talk about it we can.

That type of logic cannot be flipped because it is fundamentally sound. Outrage can always be flipped - if you're outraged at something, someone, somewhere, will be outraged at something you think is good too. You cannot wield your outrage as an argument, it isn't. Because said outrage has been used to systematically oppress all kinds of people.

I.E. "Oh being gay isn't moral! Our good, proportionally important moral principles tell us as much! It offends us all, I am outraged at this immorality!"

Why anyone would ever think relying on such flawed logic that has already been proven shoddy is a good idea is beyond me.

Of course, people will disagree over the moral principles in play over any controversial issue, and that's fine.

You just undermined your entire argument by conceding that morality is entirely subjective, which it absolutely is.