Sorry mate, but what does "bumping the line" mean in this context?
The two trans people I know or that I have met in real life are/ were...
1. a mate of the wife who is a really nice guy basically but has suffered from mental illness and all kinds of hardships all his life. One day he decided he was a woman really, everybody tried to be as accepting as possible but especially our female friends were struggling since he usually displayed what we perceived as very male behaviour in social situations (mocking and shit-talking other players during a game, talking over other people, the kind of macho grandstanding guys tend to "ironically" display etc.).
2. some dude who turned up in the boardgame shop I like to hang out with. He was just a scrawny guy in a dress, but he asked people to refer to him/ her as "she". The only problem I had with the lady or whatever was that (s)he had really bad body odour due to living in a squat. My personal line is crossed when somebody forces me to inhale their stench, so fuck that asshole.
I don't want to give you the impression that I am trying to invalidate your argument, I'm not making any generalized statements about trans people. I'm sure the rate of assholes to good people is just as high/ low in the trans community as in every other demographic.
Referring to what Spacehamster has said, I don't think that the fact that people are confused about words (although that certainly plays a role) is what all the arguing is about. My guess is that in most societies, social norms that are tied to sexual identity are rather strict, and a failure to conform to these norms is sanctioned rather harshly (depending on which milieu somebody belongs to). Also, since the 1960s, many conservative core norms have been challenged by progressive movements (and I'm using the term neutrally here), and this results in a feeling of insecurity among those social groups who have, on the average, not benefitted from this process of advancing individualisation. This is the reason that people talk about "the good old times", when in reality, almost everything (crime, drugs including alcohol, violent deaths, a lack of individual freedom) was considerably worse fifty years ago.