I will add to the rest of the posts answering this.
"Why aren't people more angry about other things like the gender pay gap and domestic violence?"
It is the SEX pay gap borne from people with a female body, that being the one that has been formed around the production of large gametes, regardless of whether that body has, will or is producing those large gametes, being negatively discriminated against because of their body.
However, at the moment there now lacks clarity in this discussion. Because if you have a mature male transitioner in a senior position in an organisation, this will skew the statistics. Get enough of them in a small sector that is predominantly male, and the level of discrimination is hidden or can be seen as going in a falsified direction.
Look at boards that are supposedly 'sex balanced'. There was one not so long ago that had 75% male representation. The latest Scottish case was shown that the EA wording allowed this to be accepted.
Why would you (general you) allow something that should be one of the priorities to be then diffused by the inclusion of people that should have their very own goals and monitoring to make sure they are not discriminated against?
I don't believe I have ever seen a poster say that trans people need to have campaigns to fight employment discrimination, just that male people should be considered male where it counts. And for every instance that sex matters in the work place.
Domestic violence is another area you mentioned. Absolutely domestic violence is important to fight and to provide support for. How do you do this when males are then included in the very support that a victim who is a female person who needs to be away from all males at that time? In shelters, in support groups. Some women are fine with it. But why would you (general you) advocate for a solution that excludes the very women and girls that need those spaces to remain single sex.
And messaging. If you remove the use in messaging of plain English terms of woman and girl and use generic terms such as 'people who experience domestic violence', you will exclude some of those most vulnerable due to language barriers. Better to have targeted messaging, with multiple applications of that message in a campaign than make it an all size fits approach.
Statistics apply here too. Why would you (general you) collect statistics that may make trans people and their needs hidden? And increase statistics for women? It is really important to have clarity and accuracy so the correct support can be developed to meet the needs of everyone.
However, it is the support of domestic violence victims that require the specific needs of women and children that needs a very clear definition of what a woman is.