As Jaime said, I am absolutely certain that it has most, perhaps excludingly, to do with Bitterness.
Bitterness that in turn causes the sufferrer to, for instance in regards of online boards, deliberately misread what other people say, as an excuse to pick fights, hence having an excuse to "letting of steam", so to say.
And it is not only in the Trans-Community this is a phenomena, but also the Gay Community.
There are ofcourse many, many gay and trans-persons that are warm and absolutely wonderful people- After all, my best friends have been "Varianted", but some of those in the communities... Wow, is all I can say.
They are so extremely bitter that you are just stunned, really, and they pick fights with everyone.
On the other hand, I have found that those that are, often lacks self irony and humor, which is both very important factors to handle the everyday life if it is a life that comes with more difficulties than usual(Discrimination, Body dysphoria, and so on).
So remember, folks; Humour, humour, humour and LOVE yourself.