Flags are symbols, full of historical meaning.  Just ask Emily Thornberry.
Following the despicable shootings in Charleston, South Carolina last week, there has been renewed debate over the Confederate Flag, the banner under which the secessionist Southern states fought the American Civil War.  Some people claim that the flag is simply a symbol of Southern culture and ‘heritage’— that flying that flag is merely an expression of an independent, libertarian spirit.  But that is disingenuous.  The Confederate cause was explicitly racist, about fighting for the right to subjugate black people.  Ta-Nehisi Coate catalogues the unequivocal words of those men who rallied their fellows to the ideology of white supremacy, and argues “Take Down The Confederate Flag—Now“.   The recent discussion has unearthed this article by Christopher Hitches from 2008, where he excorates the former Governor of Arkansas and (at the time) Presidential Candidate Mick Huckabee for lauding those who would fly the Confederate flag.  A “straightforward racist appeal” for votes, Hitchens called it.
On a more positive note, watch this wonderful TED Talk, done in the style of a radio show, by Roman Mars (my favourite podcaster).  His show, 99% Invisible, is all about design, and the talk is about the importance of flag design.

Roman outlines the principles of good flag design, draws attention to some good city flags, some bad city flags, and some truly terrible city flags.  He also explains why we should care.

A well-designed flag could be seen as an indicator of how a city considers all of its design systems: its public transit, its parks, its signage. It might seem frivolous, but it’s not. .. Often when city leaders say, “We have more important things to do than worry about a city flag,” my response is, “If you had a great city flag, you would have a banner for people to rally under to face those more important things.”