The second half of the cartoon suggests that instead of celebrating Columbus Day we celebrate Bartolomé Day.
Bartolomé de las Casas was a Spanish historian and one of the earliest European settlers in the Americas. He owned indigenous peoples and had an encomienda. An encomienda is a system in which European settlers were given indigenous peoples as slaves in return for their "protection" and with the understanding that they would be taught Spanish and immersed into the Catholic faith.
What differentiates Christopher Columbus from Bartolomé de las Casas is that Bartolomé had a change of heart.