My understanding is that the cartoon is based on a cartoon of Lyndon B Johnson from decades ago. However, the cartoon uses the common metaphor of taking a “pound of flesh” from something to make it’s point.

That metaphor is attributed the character Shylock from Shakespeare’s Merchant of Venice. Shylock is considered by many to be an offensive stereotype of a Jewish person that is sort of “tolerated” when used in a historical context, but not otherwise. i.e. if you call a Jewish person “Shylock”, expect rightly to be called a racist.

Take the character and Netanyahu, smush them together and bam: antisemitism claims.