I grew up in Colorado, where there are no Confederate statues that I know of, and yet I still managed to learn about slavery and the Civil War.

This isn't a freedom of speech issue.  People are free to express pro-confederate views if they wish.  The question is whether or not certain monuments, which can be seen by some as glorifying traitors and slavery, should be displayed in public areas (or on government grounds).

If there's been any attempt to rewrite history, it's being done by people in the neo-/pro-confederate ilk:

https://www.washingtonpost.com/posteverything/wp/2015/07/01/why-do-people-believe-myths-about-the-confederacy-because-our-textbooks-and-monuments-are-wrong/?utm_term=.38b951ff4f00