I don't understand; why do people defend things such as the confederate flag

[Aroura]

Because the south wanted independence specifically so they could continue the practice of slavery. 

The colonies wanted independence from unfair taxation.

Apples and oranges.

They South wanted independence from the North for other reasons besides just slavery. I know this is a subject of debate between historians, but I don't think it's fair to say it was a sole reason.  

Since the Confederate flag is offensive to so many people, I think out of respect for those people it would be better to stop waiving it around. But at the same time, I'm not going to accuse someone who does of being racist/pro slavery if they are saying the flag does not represent those things to them. I may say they are insensitive, out of touch, etc... but not racist.

There was also more to the colonial rebellion than unfair taxation without representation.

I was discussing the main, driving forces.  I at no time claimed these were the only reasons.

To try and downplay the role that slavery played in the civil war strikes me as odd. Why are you so eager to defend the southern states on their stances on slavery? 

I'll let the first state to secede speak for itself
"On Dec. 24, 1860, delegates at South Carolina’s secession convention adopted a “Declaration of the Immediate Causes Which Induce and Justify the Secession of South Carolina from the Federal Union.” It noted “an increasing hostility on the part of the non-slaveholding States to the institution of slavery” and protested that Northern states had failed to “fulfill their constitutional obligations” by interfering with the return of fugitive slaves to bondage. Slavery, not states’ rights, birthed the Civil War.

Declaration of the Immediate Causes Which Induce and Justify the Secession of South Carolina from the Federal Union