So it's rude for her to ignore the rule, but also rude for her to ask that the rule be changed? So what exactly is the LW supposed to do? Suck it up and comply, even though she had no say in making it?
As others have said, what she is supposed to do is to discuss with her husband her discomfort -- and I'm not saying it's unreasonable, even though I wouldn't find it more than a minor inconvenience -- that his membership in this club requires her to leave the house on the evenings he hosts. Then they can decide whether (1) he will quit (2) she will accommodate or (3) he will ask if the rule can be changed.
But the problem is that her husband is doing something that bothers her, not that the club rules are rude or unfair to her.
Otherwise, it's like saying that no clubs may ever exist that have any rules or requirements that affect any non-members.
I agree she should absolutely do this. But what the husband refuses? What if he tells her "Too bad, I like this club. The guys are coming over at 6pm. Make yourself scarce."
Is it still rude if she ignores the rule in this instance?
I think both of them are rude. In the case of the bunco situation, Amy (the member of the bunco club) was rude for having her husband there when she knew he wasn't supposed to be there. The husband was rude for hanging around when he also clearly knew he didn't belong.
Now, in the case of Amy, I kinda wondered if hubby had just decided that day to not clear out, or if she'd just told him that day and he'd said no. In other words, if it all sort of played out at the last minute and there she was with 11 women coming over and a husband who wouldn't budge.
But if she'd come home from her first bunco meeting, six months earlier, and said to hubby, when it's my turn to host you'll have to clear out and he'd said, "uh-uh, not gonna happen" then both of them were rude for going against the club's established norms.
And by the same token, in the case of the Dear Abby letter, both the husband and wife know the rules. It's up to them to work out if they can or cannot abide by them. If they cannot, then husband needs to let the club know. They can agree he doesn't have to host. Or they can agree that they'll make an exception when he does host. Or they can not agree to any of that and he'll need to drop out. But deliberately flouting the club's rules is rude, regardless of the reason.