Something remarkable has been happening to me in the past 19 days. Wherever I go, no one launches abuse at me. When I open my mouth to speak, I am received with civility and the occasional "Have a good one". I am not attacked or intimidated. Where have I been visiting for the past two and a half weeks? Philadelphia. And where do I live? London. Here is a scenario from my adopted hometown: a month ago, I was travelling on a double-decker bus. A well-dressed woman boarded with her son, respectable in his school uniform. Ahead of her was...