The idea is to report all the facts that at least a substantial minority of the public believe to be relevant, regardless of which way they swing politically. All of those facts qualify under this standard, and also the ones I suggested as well. If you leave out the part about Chicago being a Democratic stronghold city, half the American public are going to be yelling that fact at the article and concluding that the writer is biased. And if you leave out the comparison of American gun violence to other countries, you'll have the same accusations of bias coming from other readers.

If you want to preempt those accusations of bias, then you need to cover your bases and present all the facts that the public may believe to be relevant. Even those facts which you personally believe to be irrelevant distractions from the narrative you prefer.