"Hell, it wouldn't surprise me if somewhere there isn't a chapter of the KKK made up entirely of transgender people."
Wikipedia estimates that there are 5k-8k members, so while there may possibly be enough members to make up a small chapter, it is unlikely they would live close enough together for such an arrangement to make sense.
I've met some TSs in person, and a minority (not a large one, but not trivial) have insisted on the necessity of expressing within at least some gender norms, at least those who identify as men (I don't know how they would react to third/alternate/free genders), and a contingent of them would keep getting the gender wrong. It would be hard for me to compare these kinds of numbers with the general population, because (1) I don't interact with the general population in the say way (not that I intend to treat people differently, but I'm waiving some of my usual requirements for talking with other people when I'm attending a gender association meeting or the like, and the purpose for gathering is usually a bit different than my other gatherings), and (2) TSs and the general population have different experiences. However, if I am expressing in a particular gender nonconformist way, I would feel less likely to face violence from random TSs than random people, so at least on some level I wouldn't want to overemphasize the intolerant TS faction -- granted, this is a perception based on some level of prejudice, but I'm inclined to think that even bigoted TSs would generally at least have some sympathy, even if they're getting it wrong.
Like with Pica, I'm not particularly concerned with the words as much as the attitude behind those words. If you can politely notify a person about your gender, and they'll get it right in the future (with perhaps a flub or two along the way, followed by some humility after being corrected), then I think the person can be good to work with. If you can reasonably/safely do so, it's a good idea to give someone the benefit of the doubt, because you are always going to be uncertain about their particular circumstances, and it would be preferable to give them the opportunity to prove themselves before casting a strong or specific judgment on them.
