My observation has been that people who actively work against the transsexual community do so for a variety of reasons. There is no one trigger. But they do seem to have a common root: they're influenced by cultural puppet masters.
Many people oppose the advancement of LGBT rights out of political convenience or for personal gain. These are your Fascists, your Moral Majority lobbyists/politicians, and what have you. It's not necessarily that they actually hate you, it's just that hating you is SO. DAMN. PROFITABLE. And it makes you SO. DAMN. POWERFUL. Why is it profitable, and how does it make you powerful? That's simple, and you need only read spacial's post to understand. The people that support these political figures are what spacial called "Rabble Rousers". They're disinterested sideliners who, with a minimal amount of prompting and the promise of a pat on the head, will gladly oppose anyone you ask them to and believe anything you want them to while they do it so they don't have to feel badly afterward. Anything to justify supporting the cause will do, and if your justification fosters a sense of community among the masses then all the better. Purifying the race, protecting nature's design, enforcing God's will, whatever the ignorant masses need to be told to stand in line and do as they're told (i.e. oppress the scapegoat).
Particularly well programmed drones will even engage in acts of violence against the target, though they may do so without prompting from their masters. In the latter case, the masters simply pretend they've nothing to do with the incident and dissociate themselves from the situation as much as possible (this is your teary-eyed Glenn Beck expressing shock and awe that people would cut Congressmens' gas lines despite his militant rhetoric against said Congressmen). If this isn't possible, they begin to play the "blame the victim" game and declare that violence wouldn't have occurred had the victim not offended "common moral decency" (this is Pat Robertson declaring that LGBT victims of hate crimes are simply reaping what they sow, and that the violence was just the Lord showing them that they're evil). The part where this all begins to fall to ->-bleeped-<- and moves from disgusting injustice to horrific catastrophe is when a very well programmed drone seizes a leadership position. This causes the base to become extremely radicalized, and militarism against the scapegoats often follows. With adequate support, these drones can become nothing short of a world crisis and often have to be put down violently. For examples, look to Al Qaeda or the really,really bad day that Germans had on Jan. 30, 1933. Of course, in such a case people don't follow the leader out of blind loyalty anymore, they mostly follow the son of a bitch out of fear for their lives. It's a bitch when the monster they helped create bites THEM, eh?
The reason that LGBT people are common targets for this sort of thing is because we exist in small enough numbers that we can be easily set off in the "them" category in the game of "us and them". The smaller the minority, the easier the target because that target is less able to defend itself.
At least, that's what I make out of people targeting trans-people. Briefly summarized: We're easy political targets, and there's a LOT of power and money to be gained by victimizing us. When people seize that opportunity, the culture has a speaker against us. If that speaker yells loudly enough and in the right way, people will follow them. People that follow them will occasionally be so blindly loyal to their cause that they will act violently. If these violent people come to leadership positions and manage to retain followers (usually the militant elements of the movement), the ->-bleeped-<- hits the fan.
