Not talking about these issues allows the underlying bigotry to fester unchallenged.
The first panel depicts Kelly's perception of race in America in his everyday life: people of different races exist (as horrific outdated stereotypes) but there is absolutely no tensions between them. The second panel depicts Kelly's perception of what it feels like to him when racial tensions are discussed. Kelly, like most white people in America, experiences "white fragility"[2] when race is discussed. Because white people have usually not been regularly exposed to racial issues discussions of such create mental stress which can feel like a personal attack on them which Kelly depicts as a general riot. To white people, the easiest way to alleviate this stress is to shut down the discussion altogether and return themselves to the ignorance depicted in the first panel.
[1] https://i.imgur.com/vIHrvlg.jpg
[2] https://www.newyorker.com/books/page-turner/a-sociologist-ex...
In San Francisco, almost everyone expressing a political opinion will support gay rights. In rural Mississippi, many of those workers will be bringing out their anti-gay inflammatory baggage when discussing politics. I'm virtually certain that far more anti-LGBT vitriol occurs within political discussions than the average non-political conversation.
This isn't unusual either. Throughout history oppressed groups have very frequently found refuge in the apolitical world of commerce. Just look at the history of Jews in Europe. Even when surrounded by a bigoted culture, trade and business ties encouraged tolerance and cooperation. The worse periods always tended to be the points where some ruler decided that politics all of a sudden needed to be injected into every sphere of life. Just look at the Spanish Inquisition or the Nuremberg Laws.