The Irony is that the original meme is addressed by Grant's quote. Consider that Grant's statue was torn down in an act of Vandalism in San Francisco. Does his statue count in addressing the original meme?
Especially, since the meme mentions Arlington Cemetery, built by General Meigs in the front yard of the home Robert E. Lee was born within? It was a nice touch for Meigs to place the tomb of the unknown soldier in Mrs. Lee's Rose Garden.
The same Robert E. Lee whom surrendered to Hiram Ulysses Grant at Appomattox Court House?
The General that demanded, acquired, and accepted the surrender in the defeat of the Confederacy addressed within the original meme. Ponder that.
Lincoln may have written the emancipation proclamation, yet Grant enforced and secured the reality. 1st by ordering Shermans' march to the sea, 2nd by accepting Lee's Surrender. 3rd, by enforcing and implementing Reconstruction policy during his own two terms as POTUS..
A man that as you astutely point out, once owned a slave. That Slave, William Jones, Mr. Grant also Emancipated in 1859. A full two years prior to The Civil War breaking out.
Although his father-in-law owned a plantation with a small number of slaves, his own father, Jesse Root Grant was an outspoken abolitionist, and full supporter of Free Soil Party Salmon P. Chase in his run for Governor of Ohio. The same Chief Justice of the U.S. Supreme Court Salmon P. Chase, whom oversaw the impeachment of Andrew Johnson, and Reconstruction during both terms of President Grant.
https://www.theguardian.com/us-news/2020/jun/20/san-francisco-statues-ulysses-s-grant-junipero-serra-francis-scott-key