http://fivethirtyeight.com/datalab/before-charleston-not-many-people-wanted-to-take-down-the-confederate-flag/While most Southerners expressed indifference to the confederate flag before the shooting, in the wake of the shooting, nearly 2/3 of registered voters in South Carolina supported taking down the flag.
The shooting has clearly caused a sea change in public perceptions about this issue. While I suspect very few of the flag's supporters have changed their minds, many of the people who didn't pay attention to it have now realized how abhorrent it is.