Sim was supposedly resentful over the old (forgotten by most) concentration camp guard cartoon in TCJ. What Sim didn't mention (and has never confronted) is his treatment of William Messner-Loebs. Sim was the original publisher of Journey and charged Loebs fees such as a $400 a month "office fee" even though Loebs didn't live near Sim or use the office. When Loebs took Journey to Fantagraphics, Sim called Loebs and threatened him over the phone. TCJ reported all of this at the time. Loebs found the experience of working with Sim so unpleasant that he refuses to talk about it so as not to give Sim any excuse to ever contact him again.
James Van Hise