There's a point to it. It's not just "blowing up my skirt". (Seems somewhat sexist.)
Men and women really are different. Groups that include both men and women really do behave differently. This isn't a myth and it isn't social conditioning. When confronted with a situation that is related to sex, a lot of people seem to think that they can just declare that "discrimination is wrong", and that's it. A variation on this is to say that this kind of discrimination is just like that kind of discrimination, and that kind of discrimination is wrong, so this kind must be too.
In other words, every reference to "they said the same thing about racial integration", is fallacious. It may be true that people said those things, or still say these things, but that is not an element of any valid argument.
The question that needs to be asked is whether the characteristic used to discriminate (e.g. race, age, sex, gender dysphoria) actually has some sort of impact on the decision that needs to be made. (e.g. employment, marriage, service in the military.)
In this specific topic, the question is whether the inclusion of transgenders will improve, harm, or have no effect on the ability of the military to perform its mission. I will not claim to have an answer to that question. I am simply saying that if your argument is, "We have to include them because discrimination is wrong," that's a fallacious argument.