If you can't appeal to someone's logic, then it's possible you could appeal to their sense of fair play. Although they might struggle to adopt a practical or pragmatic view of a shared situation, they can at least understand and accept what's fair within it. You could be trying to create a structure within something that needs to be more flexible or adaptable. Try not to stick so rigidly to fixed ideas, attitudes, opinions, or beliefs. Getting someone on board with your plan will require you to use more words like 'we' and 'us.'