The correct answer to this open question is the following.
Unfortunately, you did not attach the cartoon. You forgot to include it. Without the cartoon, it is impossible to know what you are talking about.
However, trying to help you, we did some research and found a cartoon that portrays a man type of "Uncle Sam" writing on a bord that held from the wall of a cabin. A black man is sitting beside him, observing.
If this is the case, then what's is hypocritical about this "Mr. Solid South" cartoon is that the cartoon is referring to the application of "literacy tests" for black Americans who wanted to vote. The white "Mr. Solid South" is writing a phrase with many spelling errors.
The author tried to show that many white people were illiterate and had no moral authority to demand African Americans to be educated in order to vote.