Surveys going back decades show:
1. a lot of young people experiement
2. most young people grow up
The other side argues simultaneously that gender is fluid and that people are “born this way.” Of course, the other side is the other side because it is incapable of logic.
Is gender fluid? For the large majority of people, no. The large majority of people are strongly heterosexual and this natural orientation is usually strengthened through upbringing, socialization and the rewards that come along with family formation. These people - the normals - are the ones who are “born this way.”
For a small minority of people, there is a range of orientation from homosexual to bisexual to weakly heterosexual. (There is a category of intersexual that I will simply ignore in this post.) Almost all of these people, through upbringing, socialization and the rewards that come along with family formation, can live as heterosexuals. This will be harder for those at the homosexual end of the range, but it’s still possible. These are the people who are gender fluid (which is not to say that they are all equally gender fluid).
The other side is not necessarily incapable of logic; they just are in defense of a position that is illogical and therefore cannot employ logic.