I'm pleased to see a measured, sensitive discussion about the issue. I struggle with discussions on the subject that too often end up with daggers drawn. I'll dip my toe in and say thumbs up to Mooncup's posts and LRD's wish to get rid of gender all together, as well as many others upthread. Apologies if I repeat anything already said.
In my view, feminists see the concept and the term "gender" as a social construct, one engineered to maintain patriarchal hegemony. But, the term "gender" is used both by and in description of feminists (Gender studies, Gender-based violence, etc.) and people who feel they were born into the wrong gender/sexual/biological identity or are something other than male or female (e.g. transgender.) We're all a bit hamstrung by that term I think. Like "Domestic Violence," it doesn't properly describe what we're talking about, but because it's in common parlance, it still gets used.
While the concept of gender dichotomy, male and female, is promoted by patriarchal traditions and institutions - so should be something feminists fight against, I think many still struggle to think outside that box, to contemplate that there could be something that isn't must male and isn't just female. I sometimes wonder if the condemnation of transgendered people by some feminists is linked to a fear of losing that gender dichotomy (i.e. male = oppressing class, female = oppressed class,) that supports their analysis of gender-based injustice. Dunno.
If from a very early age, you are aware that something "isn't right" in the gender/sex identity that has been assigned to you, the only viable alternative would seem to be to transition to the opposite gender/sex. I keep thinking of the essay by John Stoltenberg about how different things would be in a world where we truly accepted and valued many forms of body shape and sexual characteristics. But, we aren't in that world. For intersexed and/or transgendered people, becoming more closely identified with the opposite gender/sex from the one assigned at birth may feel like the least worst if not ideal option.
And because they will most likely be changing after puberty, they may feel more pressure to adopt more indicators of the opposite sex/gender in order to be more "socially accepted." For example, a person born female can have short hair, no make up and androgynous clothes and still be recognised as female. Someone who has transitioned may not be able to do this without taking on additional indicators like make up, hair and clothing (same goes for FtoM transitions in reverse as well.)
In my view, this pressure to "look" a certain way to be socially acceptable comes from the sexist impetus on women to conform to a particular shape and appearance to be considered "feminine enough," and that translates over to those people who transition. The psychiatrists who insist that those who wish to transition MtoF adopt more indicators of "femininity" as a condition of being taken seriously and given access to treatment, stems from this, imho.
Linked to Mooncup's 12:17:16 post, I feel uneasy with what seems to be attempts by some feminists to define and control what a "genuine" woman is, one because it seems very unkind to those who don't conform and two, in my book it too closely replicates the messages and mechanisms in patriarchy that also seek to define what a "genuine woman" is - based generally on adherence to some ever-shifting, impossible feminine "ideal."
Perhaps it's not surprising on this forum to hear many women describing their sense of identity as a woman, as a female being connected with having a womb and the capacity to carry and bear children. That's something neither men nor those who have transitioned MtoF can do. However, there are many women who either don't have the capacity or inclination to bear children, so imho, definitions based on reproductive functioning can be both hurtful and excluding for many women.
Someone either here or on one of the linked threads said that they were primarily concerned as a woman with the struggle for women's liberation, and that makes sense. However, feminists can and do demonstrate solidarity with the struggles for justice of other oppressed groups. They recognise that similar mechanisms of oppression can be used against many different groups and that individuals often identify with more than one disadvantaged group.
I have to say I've been startled though by some of the ill-informed, crass and hurtful terms used by some feminists when talking about transgendered people. Maybe folks think they are being witty and clever, but in my mind, the use of crude remarks about genitalia or personal insults is just appropriating the tactics of the oppressor and undermine any constructive arguments being put across.
(Have my crash helmet on.)