HF, it represents an anti-common man* rebellion for the purpose of defending white supremacy and elite mercantile interests. They started wars that caused millions of deaths all because they couldn't accept "Others" having the right to democracy and self-rule. Hateful white northerners waved it proudly during the Know Nothing era to defend segregation and legal discrimination against most anyone who wasn't a White Protestant. It is also waved by the KKK and other white supremacy groups.
To have it up on a state capital, which is public property, hundreds of years later is beyond unreasonable. Citizens have every right in the world to use it as they wish. If people are not actually upset about it being on a state house, that represents a sad state of affairs.
*Which is totally ironic because the people who defend the flag are the so called "anti-racists".
I took some liberties here, but yeah you get the idea. Horrible Flag.