Let's get the obligatory shit out of the way first - obviously this decision is Blizzard's to make, they're the artists and changing their art is their right. Far be it for me or anyone else to argue that they have some sort of moral obligation to design the game a certain way. I want to make clear that the focus of this comment has nothing to do with artistic rights.
But I do have a question; what was the POINT of removing the pose from the game? I highly doubt that a team who have been toiling away on this product for all this time only just now did a double take on that animation and decided it wasn't appropriate. I'm sorry, but this is obviously not the result of creative impetus, it was a reaction to criticism.
Now taking constructive critique is absolutely part of the creative process, so with that in mind let's examine the critique and determine whether or not it is, in fact, constructive.
The argument, it seems, is that Tracer deliberately flaunting her sexuality is out of character, and reduces her to an object.
Key Element 1: Tracer's Character
So from what I can gather, Tracer could be summarized as an innocent, spritely prankster. A pretty typical Chaotic Good Rogue; the optimistic adventurer type. It's true that I don't really see where showing off her butt springs forth from that description, but I also don't see why it couldn't.
Assuming that a character like this couldn't display flirtatious behavior strikes me as a fallacious assumption. For the most part, sexuality doesn't seem to be a theme in Tracer's character, but sex is a powerful motivating force in human behavior, so strong that it is reasonable to assume that, even though it isn't immediately apparent, sexuality IS a part of Tracer's life.
There is nothing in the character to suggest the nature of her relationship to sexuality, but assuming that she WOULD NOT be open and expressive with it is just as unfounded as assuming that she would.
Key Element 2: Defining Objectification
Objectification is a word I have a conditioned distaste for, because it's a word so often misused that it's become difficult for me to decouple it from it's memetic counter part.
Objectification simply means that you perceive a subject as an object. In other words, when you don't respect or acknowledge the thoughts and desires of another outside of the context of your own. It's when the only thing important about a person is your relationship to them - in your subconscious they don't exist when you're not interacting with them; it thinks of them in the same way you would think of a tool or a piece of art.
You may still value and care about them, hell, you might even care about them MORE than you care about yourself, but during this whole process you never stop to consider that their feelings and perspective could be alien to you.
There is nothing about this behavior that directly relates it to sexuality, but when you hear about objectification, it almost ALWAYS in the context of sex or sexual desire. A lot of people behave as though the fact that their behavior does not specifically reduce women to sexual objects, that they are incapable of objectification entirely.
This fallacy is ASTRONOMICAL, especially considering that objectification is a necessary psychological construct in the maintenance of sanity. Relating emotionally with every person you meet would drive you insane with guilt and obligation.
Here is a list of people that are objectified CONSTANTLY:
Clerks
Waiters
Delivery Boys/Girls
Bankers
Lawyers
Doctors
Politicians
Musical Artists
Actors
And so on
You don't have a problem with these people; you don't think less of them. They're just the people that you know with whom you are not close enough to personally empathize with.
All of these people have jobs that revolve around the service of other people in a professional setting; jobs that require them to interact with large numbers of people without taking a particular interest in any one of them. Some of them do this in person, some of them do it via media. In either case, your relationship is defined by what they can DO for you.
Expecting any sane human being to form a deep emotional bond to someone within 5 seconds of meeting them is nothing short of ludicrous; objectifying someone on first contact is, in fact, totally normal.
Objectification only becomes a problem when the person in question's subjectivity is permanently neglected - when you are unwilling to consider them as something other than an object.
Objectifying a woman sexually does not mean that you merely take note of her sexual appeal, it means that you do so at the cost of everything else. It is not wrong or hurtful to simply take note of or act upon physical desire as divorced from emotional intimacy; no one has the right to tell you how you're supposed to feel.
Conclusion
The prevailing preconception I see with the argument is the exaltation of sexual expression above any other expression in terms of importance - there's all this baggage the writer seems to have about sex that they can't even conceive of being separate from it. So Tracer's character is bubbly and friendly; why does that preclude her from flaunting her stuff? They seem to think that just because the pose is titillating that it will distract from everything else the character has to offer.
This is a common mistake; a lot of people seem to think that when you're drawn to someone's appearance you're dismissing them as a person - but why?
Is it really so difficult to appreciate one thing about a person without dismissing the rest? Is it really so strange that their appearance is what you initially value, considering that it's literally the first thing you see? Does interacting with someone on the basis of that first impression make you incapable of potentially developing deeper appreciation for them? I don't think so; people befriend their waiters, bankers and lawyers all the time - why are these emotionally distant interactions all considered perfectly normal and healthy, but interactions based on sexual desire are so often bemoaned?
Why is it so offensive for a character to be designed with the intention to titillate?
Ultimately, I don't think the critique in question is particularly useful; it seems mired in dogma and devoid of nuance. Again, Blizzard has every right to make whatever game they want to make, but I don't think taking a critique as illogical as this seriously reflects well on them.