i wouldn't blame a flag for anything. most people wouldn't.
you could probably take a stab at blaming culture though, because in this case a flag can be emblematic of culture. the same culture that celebrates an economy based on slavery (aka institutional racism, aka "history"). the same culture that gives a gun to a kid like Dylann Roof for no other reason than that's just what happens. the same culture that often exhibits pride for willful ignorance and isolationism. stuff like that. so yeah, when this kid posed with his flag, it was because he was repping his culture, not because he's a flag enthusiast. don't blame the flag.
as far as the backlash against it, and all the calls for censoring history by revising existing monuments and the like, i really think that noise was created or at least magnified by the fact that they decided to keep flying it while the state flag was lowered to half-mast immediately after the shooting. nobody could understand that, and despite the explanation that was provided i think it kicked off a lot of dialogue about what the flag "means" today.
finally, i'm not sure i know enough to consider this shooter mentally ill. disturbed, sure, but i don't think it's as clearly clinical as it was in, say, Adam Lanza's case. as far as i know, Hatred isn't a medical condition. not one with an over-the-counter prescription, anyway.
EDIT: OP was pretty funny btw, nice find BB.
// another EDIT: my intent here wasn't to disparage culture, so i hope it's not read that way. i just think that anyone who grows up in an echo chamber of beliefs will come out the other end somewhat deficient by definition. and i suspect this deficiency directly contributed to Dylann Roof's actions.