Ok... First of all, you have the right to your opinion.

However, I have to disagree with your position on her non Japanese fans. They bought tickets and hopefully her albums/singles. They have a right to be there as you do. Even if they "act" Japanese, who cares... That's what they decided to do. If they happen to love anime or say random Japanese words, that is their decision. I am a white male who got into Utada after listening to a song of hers. I don't say Japanese words randomly unless it required of me when explaining or discussing something Japanese related. Yes, I am a little embarrassed of using words I may or may not even be pronouncing right, but that is out of the fact of trying to find the right words in English to say. ( which I end up having to do anyways because the person I am talking to is not familiar with Japanese)

However, My love for Utada is not because I just an anime fan. I was raised to grow an appreciation for cultures outside America. I live in Spain when I was five years old, spoke fluent Spanish, and was exposed to notion that not everything in the world works the same way as America does. This realization I had instilled in me, kept growing well into adulthood. I may not know what Utada is singing in Japanese but I feel comfortable in listening to her songs. Does that make me a "wannabe"? No. It makes me a cultured person in knowing my taste are not all american. I like songs in French, German, Italian, and Korean, to name a few.

In closing, you are going to encounter people who displays their love for a culture even though their skin tone doesn't match it. It's a decision they made of their free will. You don't have to agree with it but how would you feel if someone accused you of straying from your heritage and expect you to reinforce the stereotype that has been attached to your race for years? Don't knock someone behavior if you don't want the same thing happen to you.