The bit about "Northern Aggression" is more often than not a bit of fun. Anon here >>2729622
has it pegged perfectly. Although a serious historical observer would notice a lot of the North-South cultural tension has (non-exclusive) roots in Northern attempts to legislate away slavery and the slave trade in the US in the early and mid-1800s, it is almost always a joke.
However, the "Lost Cause" was less of an effect on the South than has historically been true. Is it a lost cause for Northerners to erect monuments to lost battles in the Revolutionary War and War of 1812? Like I said, the South has always been more interested with its own internal culture than with any larger American national culture. This can be seen with attempts to tie the Confederacy to earlier Southern independent states, via symbolism (Bonnie Blue flag - Republic of West Florida, for example). The modern South does the same thing. We reminisce on our history. Doesn't matter that the surrender occurred at Appomattox. We reminisce all the same.