I obviously understand that some people look at him through the context of someone who killed political opponents after the revolution. But others look at him as a figure to be emulated because of his work with the poor and undereducated.
u/ainrialai outlines the controversy of Che Guevara here, addressing Guevara’s controversial views and statements. I don’t have much of an answer on why he’s on posters and t-shirts though.