Your friends and "friends" haven't reacted right and your parents aren't being appropriate either. But you need to understand; of coirse they wouldn't take this seriously as it was blurted out in a weird context and reported to them the way a nasty rumour is.
Many, many parents tell themselves what their child is going through is a phase when they don't like it. It's a defense mechanism. "I don't know what I would do of this were the case. It must be a phase." I cannot deal with it, therefore it must be false. We all do it from time to time.
Once you manage to calm down and regain the ability to discuss it seriously (as mentioned above, a free listening phone line is a good option), your next move should probably be to go see your parents and discuss it in an adult and calm way. I'm sorry, but so far, the way you've dealt with this has been quite typically childish, teenager-like. And true, teenager do have phases. I still remember my white magic and demon hunting phase very well, as well as how it made my mother think I might have had psychosis.
Talk to them maturely, calmly. Possibly, be even more mature than they are. Ask them why they think it might be a phase, and attempt to explain to them how real and important the issue is. Asking questions is generally the way psychologists do things. I'm not an expert, but I think it gives a mature impression, and is going to lead to fruitful conversation more than an accusative approach (YOU think it's a phase, etc.)
