South Carolina will only honor resident permits from states that have as strict, or stricter, requirements to get a CWP as SC does. GA doesn't require the 8 hour class nor the proficiency qualification so SC won't honor GA's. GA won't honor SC's because SC won't honor GA's. As a SC resident, though, I can get a NH non-resident permit which GA will honor. People visiting SC cannot do something similar, though, as SC only recognizes resident permits from reciprocal states, not non-resident ones.
For anyone who lives in SC, as well as anyone who wishes that they could travel to and carry in SC, please join: http://www.scfirearms.org/
They very actively fight for gun owners' rights in SC and also work toward making SC honor CWPs from other states. If you want them to be successful, they need your help.