Wow, that's bad
I can understand he tweeted about that. I live in one of those "places" as well (not in London, but a neighbourhood in a big city mostly populated by people from Turkey, Marocco, India, Indonesia and Surinam etc.), and I've never EVER heard anything about tourists being robbed or ANYTHING like that.
People are just weird, and haters will always hate
On to a less serious matter...
Okaaayy....