smakers
The problem with your comparison is the fact that it's obvious that you think there is always something inherently wrong with being trans. Yet, when you look at it objectively, there really isn't a problem with it, much like being gay, etc. The problem with the trans issue, is that not everyone ends up looking attractive - as a result, they get made fun of.
This is where the argument gets cloudy - however, these people don't choose to look unattractive; it is merely a result of their biological disposition. The only reasonable comparison to make, is that when obese people react to depression by eating a lot, they, as a result, end up looking obese. They indulge their desire to eat much like a transperson desires to be percieved as the opposite gender. What is wrong with the obese person, is that they can easily equalize their desire to eat by simply exercising more, so they don't suffer any negative consequence. There is obviously no such simple solution for a transperson, thus your comparison makes no sense.
The only exception is when the obese person in question has a specific problem with their body that makes it extremely hard to lose weight to the point where they will only gain weight. However, this problem is rare enough that one can assume there is really no real reason for most people to be obese.