A memorial in Denver's Riverside Cemetery was built in 1971 by the Sons of Confederate Veterans.

It wasn't built more than 100 years after the war by somebody's "sons." Sons of Confederate Veterans is a heritage group. (It's a white nationalist pseudo lobbying group today.)

A headstone there says it's in honor of Colorado's Confederate veterans for fought during the war.

Sorry, there's no such thing as Colorado civil war veterans. Colorado became a state in 1876, after the civil war. Colorado f/k/a Kansas was a free state and had few Confederate soldiers this far west.

15 Confederate soldiers are buried there, along with 1,300 Union soldiers.

Where's the union memorial? The 1971 memorial donated by a white nationalist lobbying group at a cemetery in a free state that purportedly has 100x more union soldiers buried than confederate (if there's any at all, which is unverifiable).

Doesn't seem super defensible to me. Sorry if I seem upset. Don't really take the issue personally, just offended by your offhand comment that glosses over some of the historical context.