Well I'd say try not to take it personally (which I know can be rather hard). If you can get through that part, there may be a way to win them over to your point of view. But it's also possible that you're never able to see eye-to-eye. In my industry this is euphemistically called "creative differences" and one side or the other leaves the project. If something is causing boiling rage every time you even think about it, it might not be worth continuing.
Obviously I can't determine who is "right" in this situation because I don't know all the details, and I can't hear from the other side so I have no idea what their point of view is. All I can say is that if a consensus can't be reached, and tensions are high on both sides, you may just want to back away for a bit. They may not be in a situation where they think they can do the things you want them to, and it's not worth arguing about. You see it one way, they see it another, and ne'er the twain shall meet.
Or it's possible that they'll sleep on it and realize that what you're saying is good and they'll apologize and everything will be fine and dandy. That would be nice!