Radical Feminism (one concept) is somewhat equivalent to separatist feminism, which takes it as axiomatic that women making decisions under the influence of men are not free to make decisions (they're the "all sex is rape" school). Given that, they historically[0] tended to see trans women as male invaders of a female space, which makes them de facto transphobic. Transphobia is not a typical property of feminists who happen to be radical in their views - if anything, it's the opposite (radical feminism is a second-wave school which had its peak in the 70s).
Not all people who call themselves radical feminists believe that "all PIV is rape" (notice how you equate sex with penis-in-vagina intercourse). You forgot to provide a link to that [0], I'll give you one: http://againstallevidence.wordpress.com/2011/04/11/cant-we-a...
I didn't mean to imply (and I don't believe) that all radical/separatist feminists believe that, but that the idea originated in that movement. I don't equate PIV with sex but didn't want to add jargon to what was meant to be a 101 post. Hence quotes.
Any time. I believe there's a high amount of nuance to the writings, activism, and ideas referred to by the phrase "radical feminist," and without noting it, it becomes very easy to get the wrong idea about the whole thing. "All sex is rape" and "all PIV is rape" are two vastly different statements in the context of this politics.
