Being born and raised in Alabama, I will speak from the perspective of one who actually likes the flag and what it means in both American history, and on a personal level...
For starters, it is NOT a symbol for slavery or hatred. Some will interpret it that way, but they do not understand where the South was coming from. The Southern states were in the Bible Belt, and countless laws and ordinances were based off the Bible, including slavery. The OT spoke of having slaves and it being perfectly legal and moral. God even commanded the Hebrews to take slaves, how to treat them, etc. The Southern states were also mostly agricultural, with the Northern states being industrial. To work massive plots of farmland, slave labor was "a must"...or so they thought.
Slave and plantation owners made up for approximately 5% of the Southern population. Only the wealthy could afford slaves and hundreds (or thousands) of acres of land. Most Southerners were poor farmers that tried to scrape by with their families, and did not own slaves. They were lucky to have the clothes on their backs.
The Northern states, being industrial, did a lot of trading with Europe. They also wanted the Southern states to buy Northern goods almost exclusively, so they jacked up taxes and tariffs on European imports, and then raised prices on their own merchandise. When the Northern law makers said "Territories can't have slaves," that was the final straw.The South protested and eventually said "screw you...we'll secede and form our own trade pacts, and do things our way." When Lincoln ordered the Union Army into Virginia, he was invading a foreign country. That rallied many Southerners to come to the defense of a sovereign nation under attack. It also gave them something to do, wages, clothes, food, and shelter (a tent is better than nothing).
Slavery and the abolishment of it was not a concern for Lincoln or the Union Army until two years after the Civil War started. Lincoln wanted France to blockade the eastern seaboard as well as the Gulf of Mexico (like Mobile Bay, Alabama). The French, who helped the American Colonies win independence from England less than 100 years earlier, was an American ally. They agreed to help, but only if slavery was made illegal and all the slaves were given their freedom. Thus Lincoln's Emancipation Proclamation of 1863.
I had ancestors who fought for the Confederacy. Not a single one of them was ever a slave owner. They fought because a "foreign army" had invaded their homeland, and they felt a sense of duty. To put it in perspective, think of the movie "Red Dawn." The Union Army was North Korea and the Wolverines were the Southern rebels fighting the invaders. That is exactly how many Southerners felt. They could have cared less about slavery...95% did not own slaves.
Many people this day and age see the Confederate flag as a symbol of States' rights. These are the same people that want a smaller, less intrusive federal government. They don't want "Big Brother" having its fingers on every little detail of life.
So, for many people, especially long time Southerners, that flag is a part of our heritage. To ban it would be along the same lines of saying:
No more MLK Day. Screw your heritage.
Spanish is illegal to speak here. Screw your heritage.
No more Irish pubs. Screw your heritage.
(you get the idea)
Now let's talk about slavery and what is NOT taught in school. Many people do not realize that the Europeans who went into Africa and started shipping slaves over to North America, did not actually conquer the natives and enslave them. No, no, no...African tribes would be at war with each other and the victor would enslave the loser, sell them to the Europeans in exchange for goods (clothing, food, alcohol, weapons) and that is how the slave trade got started in North America. Blacks would enslave other blacks and sell them off.
All of that being said, do I agree with slavery? Absolutely not. It is an inhumane practice that should be illegal, period.