He was linked to the Nazism explicitly, and not merely by being a rigid military type, first by including a German Luger in his gun collection and secondly, in case we miss that subtle point, a plate from his china collection had a swastika for ornament.
FreeTally, no matter how short the gay couple appearances are, they are central to the story, because, in a movie about disfunction, they are the only happy well-adjusted people. They represent the beautiful, peaceful, healthy, live-and-let-live, white-picket-fence American middle class life that everyone else doesn't have. They are in the movie to provide a contrast to dark and corrupt sexuality of the teenager girl, who brings everyone to ruin.