Why are people so bitchy about this?

You are not a "sicko" for having fetishes. Most people do, there is just a social stigma in place that one does not discuss such things in public/with other people. (Hence why the person you know does not want to talk about it.)
There are varying degrees of bondage and and sadomasochism (S&M - a subset of BDSM). It could be as "benign" as using a silk scarf to bind someone's wrists/blindfold them and/or the act of spanking during sexual relations. And then you have the extreme example of the "red room of pain" from Fifty Shades.
If I were to guess, this fetish has been around for A LONG TIME, its just that no one really talked about it before - and it has come to the spotlight because of this book series.
Also, as if you need reminding, you are a teenager, your friends are most likely around your age. People's view points on things change are you grow older and mature (I'm almost 30, and I am not done maturing). You will be shocked and surprised how vastly people's viewpoints on things change after you leave high school and enter college/university! My experience was that the norm went from a narrow minded view point to one of openness and acceptance for various things.
I knew liked BDSM, to a degree, from around the age of 14. (No, I was not having sex at the age of 14.)
Your fantasies are just that, yours! There is NOTHING wrong with having them. The only time I would condemn someone for having a fantasy would be they acted on one that was abhorrently WRONG (extreme example: raping a person, or child, and then hospitalizing or killing them). You are the only person who can judge if what you are fantasizing about is “right” or “wrong.”
Yes, there is a social taboo on this subject, and I know that it is hard keeping somethings you like private. If you want to try to snub this one out, maybe try to think of an alternative to something specific you fantasize about (i.e. instead of doing this, maybe I could do that).
I can understand you do not like yourself because you like this... I was raised in a fairly conservative household when it came to matters of sex – so I never talked to anyone about what I fantasized about, until I met my husband.
If you truly do not want to like/fantasize about this anymore, the only thing I could suggest is to try to distance yourself from “triggers.” (Like if reading the books makes you want it more, maybe find a different series to read.)
I promise that people do grow and mature and become more acceptant of different things as they get older. The ones who remain narrow minded about topics that are sensitive to you – like this one – are the ones that you may need to distance yourself from.
My last two cents: when it comes to matters of sexual preferences (be it positions, partners, role play, ect.), there isn't really a “normal” - there is what society says is “right” and then there is what everyone else does in private.

Okay, now we're getting somewhere, Miss Anonymous.

You need to stop listening to those girls who do not even KNOW about the BDSM lifestyle and pass judgment on it. They literally do not know what they are talking about, so their opinions are irrelevant!

50 Shades of Grey is a terrible introduction to the BDSM lifestyle because the relationship between the protagonist and Christian Grey is not healthy; it is in fact highly abusive and oppressive. Anyone from the Lifestyle detests the fact that 50SoG is giving the Lifestyle a bad name. And it is going to get someone hurt.

That being said, you have done nothing wrong. You are not a bad person for the way you feel, and you need to distance yourself from the opinions of uninformed people who do not support you. You are filled with contempt and self-loathing because of their opinions, and you need to understand and accept that who you are is who you are, and who you are is not bad.You have no reason to feel shame. Why would you want to be part of a group that is that shallow, ignorant and narrow-minded? They are wholly un-knowledgable of the subject and as such their opinions are not even fit to listen to because they are born out of willful ignorance.

You need to tell yourself that it is okay to love yourself and stop abusing yourself in this manner. It is driving you all kinds of crazy. If you accept who you are, this dissonant nonsense will go away because you will feel more at peace with yourself.

I wouldn't say you're an "effed up" teenager for liking the things you do. It's your life, your preferences, and your fantasies, you don't have to change your lifestyle for anyone but yourself if it's not hurting others. But I agree with Tim, if you think people are uncomfortable hearing about your sexual fantasies, maybe keep them to yourself? If say, you can't help it - like you're wearing your collar where everyone can see - then you still don't have to indulge them by talking about it. Just change the subject or something.

Part of the draw for you is that it is taboo...outside of the "accepted" sexual gynamistics. If you know people are going to freak, stop talking about it. If it's only fantasy, then no harm no foul. To actually do it, though, you'd have to find someone who is into the same thing. You may find that reality doesn't meet up to fantasy and you won't have your fantasies anymore. I don't think you weird or anything like that. Being tied up is a fantasy to some because they like the thought of not being in control of what happens. I don't think you're "broke" or anything like that.