I just did an anonymous donation. Nearly 1000 donors!
I got into a polite discussion about this on my CLP closed FB page. Someone (a man) shared the Eve Livingston tweets (screenshots) with this text: "It's very disappointing to see transphobia from Labour Party members who are crowdfunding to exclude trans women from all women shortlists. Trans women are women and should be included as such. As Diverse Communities Officer, I'll be making sure I engage with trans people to ensure they are included in local activity as much as possible and have a voice. Transphobia is never ok, however it's dressed up."
I responded, basically saying if you agree with AWS on the basis that the patriachal system is poorly set-up for women (based a lot on our biology & associated gender roles) then why would it be a good idea to dilute AWS with people who aren't subject to those constraints. I got a few likes and one woman posted to say she agreed.
Then a couple of men posted "Transwomen are women. No debate" - I left that alone because I thought it spoke for itself.
Then a very young woman posted a direct reply to my comment "in what way does cis women's biological bodies make it difficult to demonstrate 'commitment and reliability'???? all women shortlists and affirmative action exist because of people's perceptions of women, not because women are inherently lesser."
She had taken the quote out of context because I had said "judged within the patriarchy", so I put some basic stuff about, well, feminism 
and explained the gender pay gap etc and the reply was basically "and you think trans people don't have it harder?". So I said "I think we're going in circles, but thanks for the discussion."
I think it's really important to be measured and polite whilst putting the point across. I had a hunch I wasn't going to persuade her, but hopefully my approach will convince someone who hasn't given this any thought before and is reading the thread.