Why bother with political discussions? Everyone just gets upset or turns nasty

We need to have political discussions because politics is what drives everything in the world. People need to be engaged in how the world runs. The problem comes when, as you say, everyone just gets upset and turns nasty. That's because people far too many people hold their political beliefs as dogma rather than as rational concepts that can be discussed rationally. When people's beliefs are criticized, people react to that as if they, themselves, are being attacked. And, to a great extent, what passes for political discussion today is mostly just bad mouthing those with whom one disagrees rather than a rational, logical, fact-based examination of the issues.

If everyone turns away from political discussions, how can anything ever change and how can we find some way to build consensus about how the world should be run? A democracy can't exist without people willing and able to engage constructively.