An Australian Television Station had a poll asking who was going to win the Superbowl and why and my answer was, "The team that finishes the match with the higher score. As that's convention."
I have seen couples going to football matches where say, one partner is Scottish, English, Japanese (bit more diplomacy there) or any other and the other is Australian and they are supporting opposing teams and they have said, "We're on opposite sides over this, but it's the only time we're not united." And then, after the match, they go home and go to bed.
I also remember seeing a woman one day, who was driving a Ford Falcon but wearing a Holden (GM/C in America) singlet and I asked if she liked both. Her response was, "It's my husband's car. He likes Fords. I've got a Holden." Presumably, if they like car racing, one supports Holden, one supports Ford.
In those cases, they might give one another some ribbing or banter, but anybody who would violently assault their domestic partner because their preferred team didn't win the Superbowl is emotionally immature, even if they bet on it and lost money. And even if their partner told them to bet on that team. The best closing remark goes to a reporter who commented on the murder of Andres Escobar by gangsters after the 1994 World Cup. "They'd get another chance in four years' time, Escobar will never get another chance."