you should decline their demands before. this also raises their war support but should pay out.

So, here is another good one. I started another war. They made demands but I intended to roll through anyway. I basically defeat them but now I have to give back territory that is already mine.. and pay for it from my war score. Sorry but this cannot surely be correct?

I agree it is annoying and makes warfare more complex as it should be.

Personally I also do not like the wording "Pay .... or give ... " can easily be misinterpreted that you (left side) have to give it.

Items should appear on the according side who is to action so it is clear that they will give it. In this example all the items that could be selected should be shown on the deafeated (right) not on the left. "civ like" 

if you cannot or won't change the design, understandable and complex, please rename it: war winner: receives ... gold, capture: cityname

@The-Cat-o-Nine-Tales what do you think?

As the tooltip says, it should only be the demands on the winning side, not the demand of the losers. This is a bug clearly.