Let me preface this discussion by saying that having unrequited feelings for someone sucks. It's a painful experience, and by no means am I intending to devalue that pain. You have a right to feel hurt over being rejected. You have a right to your own emotions.
Now: let's talk about the Friend Zone.
Inherent in the idea of the Friend Zone is the thought that, after a certain amount of time and effort, you are entitled to some kind of reciprocation from the other person involved. This is not, nor has it ever been, the case. The Friend Zone thinks of people like gumball machines: if I put enough money/time/effort in, I get my reward. I deserve that reward.
Realistically, human relationships are a lot more like slot machines. You can spend all the time and energy and money you have on one and are in no way guaranteed success. In fact, if you are successful, it's a rare and lucky occurrence. When you walk away from a slot machine empty-handed, no one feels bad for you. It's a risk you take when playing the game. When you walk away from a girl empty-handed (or, y'know, with a friend, which I'm not sure why that suddenly became an undesirable thing to have), she's a "bitch" who "led you on."
I don't think I'd be nearly as upset by this concept were it not for the fact that the Friend Zone is a one-way relationship. When a guy has feelings for a girl who just wants to be friends, she's FRIENDZONING him. When a girl has feelings for a guy who just wants to be friends, she's pathetic. Just look at the way these things are portrayed in movies -- think "He's Just Not That Into You" or Bridget Jones or any number of sappy chick flicks. Wanting something with a man who doesn't return those feelings is pathetic. Wanting that with a woman is admirable and "she really should just give him a chance."
It's no coincidence that I'm talking about this right now. The UCSB attack comes from the same twisted double standard, the same misunderstanding of whether people owe you anything just because you've tried.
This guy says it best:
Angrily yours (full of lady-rage),