I'm sorry this thread is so polarised and is really upsetting people who are good friends on mumsnet and in real life.
I like and agree with the posts from www, dino, blu, respectedposters, sophable and batters. Their posts are honest and heartfelt.
I also think aloha's posts are honest and heartfelt. I think she is expressing her fear- she is clearly very scared, like a lot of people. And fear doesn't always respond to logic unfortunately.
I've recently finished some work at a place where I happened to be the only white member of staff in my office. I found that at first it was sightly difficult to get to know people, as indeed it always is with a new group of people. But I did fleetingly wonder if being white English was making it harder for me to fit in. The thought made me uncomfortable. By the end I'd got to know everyone and was having a lovely time and one colleague, X, said to me "I'm so glad I gave you a chance and made the effort with you. You don't seem like a white person now I know you." A little more probing (together with assurances from me that I am very definitely a white person and, if not proud exactly, at least quite comfortable with that, thank you very much!) and it seemed that X's perception of white people was that they were apt to be unfriendly and racist. She'd found this through hurtful personal experience and, you've got to admit, history is on her side with that one too. You can totally see why she might have been wary of me. But she gave me a chance. She fought her perception, based, what is more on pretty consistently nasty experiences of white racism, and was friendly and welcoming and helpful, not to mention clever and funny. I am SO lucky she did. It benefited me, her, the rest of the office and the work we were doing.
Looking at the bare, grim facts I can see why people might be wary of young Asian male strangers on London transport just at the moment. It is understandable that people are scared, just as it is understandable that X thought white people were 99% racist. But... it's just not good enough to just accept our fears and stereotypes at face value and not fight them. If X had done that she would have lost out on knowing fab me and I would have lost out on knowing fab her. If we in London start mass boycotts of public transport and avoidance of people because of their skin colour we will lose out bigtime. And we will be dicriminating against people like lovely sis and her family, lovely blu, her partner and son, lovely www, her son and ex, both my sons' fantastic teachers, practically all their friends, REAL LOVELY FAB PEOPLE. Not good enough.
I honestly think that everyone needs to muster whatever courage they have on this one and try to fight their fears. The big grin test is the way forward.