Agreed. If I can suspend my disbelief for aliens and ghosts, I can manage to struggle through a bad WW2 movie just to see some effects.
If the film in question is supposed to be based on a real event or person, I'd rather see a good/historically accurate movie with bad effects, than a bad/historically inaccurate movie with great effects. If it's just a generic period movie, something like Kelly's Heroes or that crappy WWII movie with Billy Zane & Michael Madsen, I don't care if uniforms, weapons, etc, are accurate.