Original post by tazarooni89This is my understanding:
Everyone has a biological sex; either male or female. It's defined based on your genes, chromosomes and reproductive organs, and it's not possible to change it. However, we also have a related sociocultural concept called "gender". It reflects the fact that males and females tend to differ in more ways than just their physical bodies. Certain things are considered more "masculine" or more "feminine" depending on which of the two sexes they're more associated with. That could includes people's names and forms of address, behaviours and mannerisms, dress and appearance, hobbies and interests, psychological and emotional traits, family roles and responsibilities etc. It's a bit less black and white and a bit more subjective than sex, it can vary between cultures, and people may conform to gender norms to varying degrees.
Some people, for whatever reason, are unhappy with the biological sex of their bodies, and experience "dysphoria" as a result of anything that reminds them of their sex. To alleviate this, they may choose to alter their bodies to resemble that of the opposite sex. But more relevant to your question, they may also choose to adopt a new gender identity. This involves behaving and presenting themselves to society according to the gender norms of the opposite sex, and expecting society to perceive them and treat them as such. Again, this doesn't actually change their sex, but the aim is to live life as if they belong to the opposite sex and to effectively forget about their real one, as far as possible. That also means they may not appreciate being reminded of their real sex.
Some people might have no problem with their biological sex and feel no need to alter their bodies, but even still, they may not conform to the gender norms associated with that sex. They might reject the idea that they automatically "belong" to a gender or that they should be expected and assumed to conform to a set of gender norms just because of the sex they happened to be born into. They may instead adopt a new gender identity as a way of expressing their personal choice and individuality as to which set of norms (if any) they want to live by and be treated by.
Now as for your question: If someone adopts a new gender identity, does it mean they actually are that gender? Well it depends what you mean. If you're using the word "gender" as synonymous with sex, then no a person cannot change their sex; a male person cannot become female, nor vice-versa. But if you're using the word "gender" to refer to masculinity and femininity as I described above, then yes, a male person can be more feminine and a female person can be more masculine.
Regarding respect, I think the idea is that we shouldn't say things that we know will upset people if there's no need to, even if they're true (e.g. reminding someone of their biological sex when they're doing their best to forget it). Having said that, I personally believe that some people take this too far, (e.g. by seeking to curb people's right to free speech, or demanding to be treated as a member of the opposite sex even when it would be impractical to do so). As with any group of people, there are always going to be some self-centred ones who think the world revolves around them and that their interests should always be front and centre.