Because most attacking us seek to do so from the alleged moral high ground.
"While most of those defending the Union position are perfectly willing to recognize that many Southerners, such as Lee and Davis, were noble individuals fighting for an inherently ignoble cause"
We do not believe it to be an inherently ignoble cause. I am not sure noble men would remain noble if they did that would they?
Well, the problem there is that that at the time of secession, it was pretty well unanimously stated that secession was necessary to protect the institution of slavery. Those of us who disapprove of that institution have a problem seeing these attempts to protect an evil institution as anything but ignoble.
However, certainly not all who fought for the South were conciously fighting to protect slavery, just as not all who fought for the North were fighting to end it, especially in the early years.
There were men with ulterior and ignoble motives on both sides, just as there were men of nobility and honor on both sides.
I just object to the continuous attacks on the integrity of Northern heroes when similar attacks are not made on Southern heroes. If you have genuine evidence of genuine corruption or evil on the part of Grant or Lincoln, I'd be interested to see it.
Not evidence that they waged war ruthlesssly. That is how war works. Those responsible are those who start wars, not those who end them. I find it interesting that some of those most appalled by Grant's or Sherman's brutality are presently wanting to kill anybody who wears a turban or speaks a language they don't understand. Makes it look like they're not opposed to brutality, just brutality practiced on "their people."