Elephant - your point at 18:10:07 is very valid. I've witnessed the greatest hostility towards trans people and even towards those who identify as men but are perceived as being effeminate, amongst men. In my view, it's an adjunct to misogyny. As you say, they despise women, and they equally or even more viciously despise men who seek to be like or actually become women. That means they are choosing to become part of the already hated group. They also serve as a reminder that maleness and masculinity aren't immutable. It's the, "well if that dude can become a laydeeee, will others think I might do that to? aaaaaaaarrrrrrgggggghhhhh" sort of thinking.
Celestina, I agree that there may be some types of experience that girls uniquely share, being born as and identified as female and growing up within a sexist culture and society. But, there will also be some girls and women who share experiences of growing up in a racist, classist and disablist society (for example) with boys and men, too. The affinity and bonds between people from those experiences are equally valid, imho.
However, there can also be an overlap in experiences - say a girl who has experienced sexual bullying and a trans girl who has also experienced sexual bullying.
And, of course there can be varied experiences even within a group of women. Teen mothers say the often feel marginalised and patronised within antenatal groups where most of the parents are older and often from more privileged backgrounds. Many Black women have felt silenced and excluded within feminist groups where the intersectionality of their oppression hasn't been recognised or valued.
I suppose I'm arguing that there may need to be a blend of spaces specifically for people who share common identities, but that may not be the "right thing" in all circumstances. And, it's dangerous to assume that just regarding something as "women only" will be sufficient to make it fully inclusive of all women, or that there still won't be hierarchies of privilege and disadvantage within those groups, whether explicit and whether or not its acknowledged.
(bit of a ramble that - off to the gym now!)