That's a hyped up media myth, things are the same now as they always have been, back in the 1800's Old London town, folk would not go out at night because of muggings & murders, and no one helped other folk out then due to the knife crime.if you get mugged people unlikely to step in if they do the crimnals human rights will have been breached.
It's all over-hyped media, stats, and hysteria these days, same as the fact that everyone is a child molester......probably more in Roman days!!