Yes, let's exclude statistics in order to normalise them. Because if we cut out the bits of statistics that sway them, we can claim the distribution is the same as elsewhere!
The parent comment is providing a better, more specific grouping that helps shed light on where murders are actually happening in the US and points us towards where we need to focus our efforts if we want to actually change the murder rate in the US. Inner city interventions will result in the greatest improvements to the murder rate, whereas focusing efforts elsewhere has literally zero chance of bringing the murder rate into line with the rest of the G8 because that's not where the murders are happening.
And all that is leaving aside the matter of whether the statement is actually true, as questioned by a number of other threads
In slums you have a completely different expectation of law enforcement and law enforcement presence, social service, education, economy, transportation, etc. In every respect except for lines on a map, slums are a completely different world. "Countries" are an obscenely coarse classification, we should always be open to more fine-grained analysis.