I don’t think there is anything irrational about the view that gender expression is in part based on stereotypes and social construction. Cross cultural and intergenerational comparisons clearly show that there are cultural differences in how genders are expressed.
It is not irrational to believe that some people are drawn to gender expressions not traditionally associated with their biological sex, nor is it irrational to suppose that there is suffering associated with being prevented from doing so, or humiliated or ostracized if they do.
What is irrational is to claim that there is no such thing as biological sex, that sex rather than gender is a continuum, and that the only difference between a man and a woman is what someone claims themselves to be.