In time I'd hope you're right about capital punishment. But my impression is that, here in the UK too, attitudes about the death penalty are somewhere where attitudes tend to take a long time to shift. The evidence is that there is still popular support for it here,though it's been ablished for many years. One of the worries about Brexit is that while we are in the EU there is no way of bringing it back, and that's not likely to be the case for long.

While virtually all developed countries have got rid of the death penalty, this has generally not been as a result of popular demand for abolition. The only example I know of where there has been a popular vote in favour of not having it is Ireland, where there was a referendum in 2001 in favour of a constitutional amendment barring any government reintroducing capital punishment. And that was years after it had in fact been abolished.

The point is, I'd see it as an issue on which differences should not be allowed to get in the way of cooperating, and the same should apply to the others.