I think the Black chick did the best thing there. Calm the Asian dude down before he did something that would have only got him in trouble.
The druggo taunting the guy would be the first guy who would scream "assault!" if he fell over. We all know the type. Had this happen to me myself near Central station one day, where a Druggo starting having a crack at a friend and myself, and then when we walked up to him, he yells: "you can't touch me!!"
I think the white fellow who changes seats (or maybe it was approaching his stop) would be criticised by many. I don't necessarily hate people for not wanting to get involved. Some of us just don;t know what to do, or fear being assaulted or worse ourselves. To many craizes in Murica.