The official death toll for the Civil War was around 625,000. The numbers of innocent civilians killed is said to be quite small -- somewhere between a few dozen and less than 1,000. But there are no actual numbers I can find to tally any civilian deaths.
The suggestion of nearly 400,000 civilian deaths is beyond comprehension, and demands some evidence supporting it.
Here's what I came up with:
It's easy, when you make stuff up as you go along. The more they argue, the more rabid they become, the wilder the claims that they make.