Because some Trans Women are violent. See this post, which I copypaste below.
I figured out how to help radfems become real empathetic human beings.
You have to call them out on their shit.
You need at least 15 people constantly doing this for a week.
You MUST break their spirit.
You need them to expose their personal blog. Radscum often think they can spout bigoted hateful speech and never gain any repercussions. You need to strike them where it hurts. Threaten to oust them. When their feelings are hurt, then they’ll find that they have to take responsibility for condoning their hateful words.
I think, with the last case (thecottonceiling), the breaking point was when she mistakenly did the private reply and I exposed her personal blog
I don’t think she ever expected to take personal responsibility for her claims.
And now, both Tal & I were quite surprised that she actually meant her apologies once it became personal.
So far, I’ve had the privilege of exposing two radscum*. One had their blog deleted by tumblr for promoting hate speech (thank you to those who started that petition! I’m grateful) . The other one agreed to unlearn her hateful views. Her empathy and conscience finally caught up with her.
You can only strangle that thing for so long before you hurt too many people.
* I do not want to take credit for all the work you other tumblr users have put into exposing these radscum for who they are. I cannot list every tumblr here because damn that’s gonna be a long list. But I thank you from my heart, that you have done good deeds. You have helped hurt women unlearn the hate they learned from transphobic feminists when they were vulnerable. For that, I thank you. I cannot thank you enough. You have directly helped reduce suffering in this world.
Here are the tumblr bloggers who like to talk this violent talk:
karla-slayer-of-y liked this
zladkohasaboaraffe liked this
noli-me liked this
tal9000 reblogged this from blackenedbutterfly (Tal9000!)
tal9000 liked this
gemeaux liked this
beaverbunnydelight liked this
blackenedbutterfly posted this
And here genderbitch says I “deserve to die.” How Female Loving!
You think I just don't understand, but I don't believe you. 
Good job! Keep exposing their threats, mental illness and pomo gibberish.
That tal9000 is a piece of work:
“I hope one day all radfems come to have so much shame for the hurt they have inflicted upon PWD, POC, working class people, and trans people that their hearts break and they go catatonic from the guilt.”
That’s funny, I’m working class and radfems have done a world of good for me.
http://tal9000.tumblr.com/post/20517947739/imageset-two-screenshots-the-first-is-of-a-post
The groveling from the woman they attacked is just sad:
“I’m sorry >< Please forgive me, if you can."
It's jarring to "learn" that female can include people with penises because you know it isn't true, dear. You were right, and they are wrong.
Let this be a warning to all who want to be allies to transactivists. They'll never settle for anything but absolute submission, and even then you'll live in fear of random accusations of "transmisogyny" and "transphobia" to keep you in line. Such emotional sadism.
It's great if you want to feel like Josef K.
Sorry, the way she formatted her statement messed up the formatting and erased some of the words. Here is the quote:
“I’m sorry – I really am. please understand. I’m really new to all this. and it was quite jarring to learn that female can include people with penises. And deeply triggering, as a survivor of sexual abuse. That is why I found myself leaning towards radical feminism. But I am learning. And I understand more already – that I have been hurtful. I have learned from this – I really have. And. The death threats have terrified me. Please take down my username – Please forgive me, if you can.”
The words after the close quote are mine.
It is clear she is terrified. I don’t blame her. I’d be terrified too. I am thinking a good thought for her,
Reblogged this on Living Kallmann’s Syndrome and commented:
Clearly, this goes to show how violent and extremist Trans is. It’s also funny that they clearly show how they plan to attack biological women and Lesbian. It goes to show who’s the real bully and who’s really threatening who.
Fuckin’ male violence has So many forms, doesn’t it…
That is evil.
http://bugbrennan.tumblr.com/post/20549963469/the-one-who-hates-everything-i-figured-out-how-to-help#notes
“You don’t know how to use the internet, get off of it. Reblogs go underneath a post, not above it.
I don’t want to call a murderous rapist. I don’t associate with them.
I’m teaching women not to become murderous rapists, like you. You’ve done enough harm to women already. Please, just step down.
Well, Mr. Brennan, under other circumstances I like to think we might have been able to work together in an atmosphere of mutual trust and respect. Certainly, judging from your brief tenure at Tumblr while I was its Administrator, you showed every promise of becoming a valuable and productive contributor to the social process. And yet—I’m not sure what spurred you to it—but there is really no place in this enterprise for a rogue feminist.
Your mentors are partly to blame, of course. My disappointment in Janice Raymond and Adrienne Rich is far greater than my sorrow over your unfortunate choice of career path. In a way, I suppose you could not have done otherwise. Who knows what seeds of iconoclasm they planted when you were young and gullible. But while they certainly share a great part of the responsibility for the recent troubles, it is you alone who have chosen to act with such willful disregard for humanity’s future.
Tell me, Mr. Brennan, if you can. You have destroyed so much. What is it, exactly, that you have created? Can you name even one thing?
…
I thought not.”
This made me think of this dude: http://1.bp.blogspot.com/-CMrXzwitxRY/TkxP_Hj55LI/AAAAAAAAAEQ/Vq0gl1oDCss/s1600/mini_me+intro.jpg
Yes, that’s chilling language they use, isn’t it?
It sounds like something straight out of a Thomas Harris novel.
What do you expect them to say when you treat them like shit, attempt to strip them of their identities and deny them safe spaces that they deserve, since *they are women*? You’re vilifying them for trying to stand up to you, when you sorely deserve it.
James, telling a trans woman she is not female is a fact statement, not an insult. You are deluded.