You are completely wrong when you say the vast majority of monuments were erected during the civil rights movement. The vast majority were erected during the late 19th century and early 20th century, when the local communities were recovered enough from the war’s damage to be able to afford it.

The monuments are there to reflect the sacrifice of resistance against an invader. The Southern States voted through a democratic process for independence, and were invaded to force them back. One can argue that they deserved to be invaded. But men will always resist an invading army, I don’t care where you are in the…

The KKK also had the United States flag. Ban it too?

The flag appears in non-American places because it’s symbolism goes beyond the way you currently view it. It is possible for people to have different opinions of symbols, and different views of historical “truth”, than yours.