Eh. With most people, it's simply that "Nazi = Evil" is ingraned in their brains. Bullseye wouldn't care, since he's bassically one notch above a serial killer, and Taskmaster is a never ask questions type, but I'm sure Deathstrike and Mandarine would care, primairilu because they're asian and thus veiwed as racially impure by the Nazis, so they'd be constantly worried that The Red Skull would stab them in the back. Nefaria would also probably worry about The Red Skull, since he's a more old school mafia type. Those guys thrive much better in a Democracy than a fascist regime. Plus, even a guy like Nefaria would find the actions of the Nazis completely apalling.