Just sit quietly. Do not clap your hands. Do not attempt to understand anyone's viewpoint other than your own. Whatever you do, cling to symbols such as the confederate flag as marks of history and deny that they ever represented anything to do with racism. Discount any feelings from people of color who note that having this flag hanging in an official capacity makes them uncomfortable. Tell people to "get over it" because it is "just a flag". Have absolutely no insight into the fact that perhaps it is YOU who should "get over it" and agree to take it down because it is "just a flag".
If you're a racist and you don't know it, then by all means, please refer all acts of racism back to the days of slavery and make sure to note that you were not responsible for this. Tell people that they should move on, that even though things aren't perfect they are so much better than they were then. Disregard the families whose unarmed children are gunned down in our streets TODAY because of the color of their skin. Remind them, again, that they should get over it.
If you are a racist and you don't know it, ask yourself no questions. Certainly don't ask yourself if you know any people of color on a personal level. Don't ask yourself if you could or have ever dared to LOVE a person of color. Because if you do, then everything gets much more gray. No more black and white answers in a world where that is all that so many people see.
If you are a racist and don't know it, tell everyone about how you don't see color. Say thing like, "I don't care if you are black, white or purple". Ignore the fact that nobody can be purple and that possibly seeing color is a GOOD thing. Forget that celebrating differences can be beautiful.
If you are a racist and you don't know it, post pictures a murderer - who attacked innocent black church members and left a lengthly explanation as to race being the primary cause of the attack - burning the American flag and note that the liberal media won't let you see this because it shows that the boy was out to kill all Americans, not just black ones. Believe that so you can sleep better at night. Please, don't notice the many black churches that start to burn after this attack.
If you are a racist and don't know it, there will never be a need for you to apologize to anyone for ways they may have suffered due to racism in this country. You can continue to deny that you have ever benefited from white privilege. You may wave your confederate flag and you may close out the voices of those who, while doing better than they were as slaves, are still struggling. Perhaps it is less painful this way, to not acknowledge that we as members of this society could be complicit in anything that caused such a long and painful legacy.
But remember this: if you are a racist and don't know it, you are free to express every one of these views and more in this country. You are not free of the consequence.
Of course, if you are a racist and don't know it, you won't see yourself in this, won't be able to hear these words. And I, as a white person who knows that I will never understand what black people face but knows that I will try, I will never understand how to engage you in the dialogue.