If F2Ms bother you (or if you think M2Fs aren't "real women"), then you're a transphobic ass and need to have it called the fuck out. And calling out bigotry, extremism, and religious and political fundamentalism is what FSTDT is all about. :)
Okay, these "radfems" and Tumblr "social justice warriors" finally made me snap, so here's some TL;DR:
I seriously don't understand why anyone would have trouble sympathizing with transgender people. I'm not transgenderand I'm hardly the manliest man who ever manned, at least according to dumbfuck hegemonic, patriarchal standards of masculinitybut I just have to imagine being born anatomically female. Something about it would feel instinctively, viscerally wrong for me, as though I were trapped in the wrong body. That's all I need to sympathize with transfolk.
It's not that being female or femininity itself are somehow wrong or inferioranything butthere's nothing wrong with being female, or with being male, or with being anything in between, or with having no gender identity at all. You are who you are. But there is something very wrong with not being allowed to be that person and express who that person isboth on the inside and outwithout fear of retaliation.
Sure, being perceived as that which patriarchal society considers essentially male does grant a person at least some male privilege. That's a self-evident property of patriarchal society, so it should go without saying. When individuals are anatomically male, self-identify as males, or otherwise present themselves as such, patriarchal society generally does not question their essential maleness unless, say, it becomes known that they lack the "right" plumbing "down there," or they subvert the normative behavior that fits their hegemonic ideal of the essentially male. (The feminists who insist that transmen are "gender traitors seeking male privilege" or that transwomen are "not truly female" are explicitly validating the phallocentric essentialism and associated binary gender norms that perpetuates patriarchal culture.)
That said, male privilege is something that is correlated with, not related to male identity. Being male does not in and of itself grant someone male privilege. Rather, patriarchal society grants male privilege based on its criteria of the essentially male. Furthermore, dismissing and invalidating the privileged does not dismiss or invalidate the underlying privilege. In fact, it is nothing less than admission of the belief that privilege is an inescapable, fundamental cornerstone of society. It is a cynical concession that people must construct a cultural hegemony to privilege themselves and disenfranchise others, lest they are met with the same fate. Moreover, rejection, invalidation, ostracization, and shame are the weapons that silence and marginalize the disenfranchised and empower the privileged, so your use of them is a disgusting love letter to the kyriarchy you claim to detest. That Nietzsche "He who fights monsters..." quote comes to mind.
I do regret my privilege, and I understand that it's not like a coupon or some kind of voucher that I can simply choose not to redeem, so I try my best to recognize it, offset it, and use it to be a voice in support of feminism. I do not, however, regret being male, nor do I apologize for it or for my male privilege. I am not sorry for being who I am, and I did not ask for the privilege that comes with it. I'd sure as hell give it back if I could.
(Edit: I've simmered down since I originally posted this comment this morning. After rereading it, I was bit ashamed by the lack of polish and attention to detail in a comment of its length, so I decided to edit it to improve some of the phrasing and fix a few grammatical errors, being the serial tweaker that I am. The contents are the same, just a bit more eloquent and grammatical. I did consider excising some parts which I wrote based on a knee-jerk assumption that the OP was a radfem Tumblr SJW. I decided against doing that, though: I felt it would be dishonest of me, so I'm letting it stand.)