I don't think it's subservience either.
I think the middle ground that the letter offers to work towards is small, positively tiny in fact, and my endorsement really doesn't go much further than "thanks for not being arseholes". The letter was really well crafted, and while I won't be going to bat for transsexual rights, as it's not my fight to to fight, I won't stand in the way either.
Feminism is still for women, and only women and it doesn't need to change anything. But male violence and toxic masculinity is a problem for us all, so if there are other people who want to challenge it, then I'm all for that. We have that common goal and I'm open to finding the common ground to challenge genderism if the opportunity naturally presents itself.