Your analysis is very simplistic. It appears to be an effort to justify your anti-memorial position, rather than to lend balance to the discussion. Here is a timeline of the US Confederacy memorials:

https://www.theguardian.com/us-news/2017/aug/16/confederate-monuments-civil-war-history-trump#img-1

Erecting monuments to the Confederacy has proceeded non-stop since the end of the US Civil War. There's never been a sustained period when American's weren't making such memorials. And many of such memorials were simply, say, erecting a plaque on a building, or naming a school or other public building after a notable event or figure from the time. About 50% of the 'memorials' during the civil rights period were schools being named after historic figures. 

The fact is, NOT ONE of these memorials is a commemoration of slavery. They are memorials to a battle, or soldiers, or public figures from the day.