I made that comment, I am British I lived for many years in the poorest area of London, and I've also lived in the Banlieue de Paris. I would not class these as "dangerous".
That's an outsider's perspective, but the reality is considerably different.
I've lived in a poor neighborhood in Texas where hearing gunshots and sirens was not unusual and where several friends were attacked by a gang in a well lit WalMart parking lot.
That's an outsider's perspective, but the reality is considerably different.