Trans women do not transition out of a desire to be feminine; we transition out of a self-understanding that we are or should be female (commonly ref… - Julia Serano

Sex is a collection of traits that, while generally dimorphic, can vary greatly in the population, and some can change over time. While the terms "male" and "female" have some utility, we should not view them as strictly dichotomous or mutually exclusive. Rather, “female” and “male” are best thought of as umbrella terms that describe groupings of people (or animals) who generally share many of the same traits, albeit with considerable variability and some exceptions.

Claims that trans women are not women often rely on essentialist (and therefore incorrect) assumptions about biology. For instance, people might argue that trans women are not “genetically female,” despite the fact that we cannot readily ascertain anybody’s sex chromosomes. Indeed, most people have never even had their sex chromosomes examined, and those that do are sometimes surprised by the results. Other common appeals to biology center on reproduction — e.g., stating that trans women have not experienced menstruation, or cannot become pregnant. This ignores the fact that some cisgender women never menstruate and/or are unable to become pregnant. Claims about genitals are similarly problematic: Women’s genitals vary greatly, and as with chromosomes and reproductive capabilities, we cannot readily see other people’s genitals in everyday encounters. If you and I were to meet, should I refuse to recognize or refer to you as a woman unless you show me your genitals? And frankly, what could possibly be more sexist than reducing a woman to what’s between her legs? Isn’t that precisely what sexist men have been doing to women for centuries on end?

Accusations that IP is inherently “narcissistic” and “divisive” have become quite prevalent among EC-centric leftists lately. [...] In addition to disregarding all forms of non-EC marginalization, accusations that IP activism is inherently “narcissistic” or "divisive" severely confuse cause and effect. After all, I’m not the one who is “obsessed” with my identity. [...] It’s the people who harbor anti-trans attitudes who are obsessed with my identity, not the other way around! While I would absolutely love to live in a world where my trans identity was not especially notable or worth calling attention to, these people insist on making an issue out of it. Furthermore, by making a distinction between transgender people (who they single out for discrimination) and non-transgender people (whose identities and experiences they respect), it is they (not us) who are the ones being divisive. Once we acknowledge this causality, it becomes clear that IP is not an expression of navel-gazing or narcissism, but rather a form of organized resistance against those who are actively trying to delegitimize and disenfranchise us.