the whole lore behind that is basically, during World War II, Peppino ended up getting kidnapped and imprisoned by the other side, specifically by a simi-rogue group of soldiers and an commander. This group didn't follow Geneva/POW to a T, and ended up forcing Peppino to fight for them (alongside many others-). During this unfortunate time, Peppino ended up having to face Maurice, shotgun loaded, and with the many around him, coincidentally corning Maurice (who was severely mutilated (entire section of his arm blown off)) into a wall. This leads to a good half minute of Pep standing over 'Rice with a whole ass shotgun pointed right at Maurice's chest, now thankfully Peppino is smart, he managed to sneakily unload his gun entirely, meaning he had the excuse to not hurt Maurice, after a loud bomb warning, the two ended up running off-. This quickly lead to a growing paranoia in Maurice mainly because he thought Peppino had died fighting the other side, not be joining them-. Now the thoughts came slowly for Maurice, after all this is his sister brother he's talking about! He cant possibly be a. . . . But being in such an unstable environment did him no favors, fear and anxiety quickly grew overwhelming until it became all he knows. Paranoia becoming a defining trait for him, dont trust anybody, nobody, anything... Not the pills you take, not the people that lead the country, not the people around you. NOBODY. And even when his mates got Pepino back from the other side, it didnt help, in fact the first thing Mauice dud was stab Pepino, 15 times. . . That little moment became the very defining moment Maurice chose hate, even if it hurt, even his he really doesn't mean the bloody knife or gun in his hand, but hey, how can he change it? It'd all he knows now.... So yeah Maurice thinks Peppino is a Nazi, simple enough when you take it at face value.