Based on your responses it sounds like Charleston is most definitely civilized enough not to blink in regards to interracial relationships...In all honesty though, these days I don't think anyone in America (except for maybe a few extremists) thinks there is anything wrong with interracial relationships. It is viewed at as normal pretty much everywhere.
If you really want to know how accepting a city is; ask this question:
How would a GAY interracial couple be treated? Would they encounter discrimination and/or dirty looks? Or, would they be treated just like everyone else?