Ok so there's no picture of the poster but generally the bias would be only showing one sides fault. For the Lusitania, the Germans were attacking with their u-boats because they were in the war zone but that side is not depicted very often.
This is true because Plessy v. Ferguson was a landmark 1896 U.S. Supreme Court decision that upheld the constitutionality of racial segregation under the “separate but equal” doctrine.
