I've been trying to work out in my mind why some exchanges about potentially controversial topics turn nasty and leave you with a bad taste in the mouth and others end up with you feeling you have a better understanding of what you think and of why someone else might see it differently.

And it seems to me that one reason is that there are different models for what is happening in the course of such exchanges. On the one hand they can be fights, trying to beat the opponent regardless, anything goes. Or they can be collaborative exercises - either collaborative in the way that in a formal contest or game your opponent is actually in a deeper sense your partner; or in the way that different people with different ideas can be involved in a joint project.

One thing that I often find irritating in a discussion, whether I'm involved myself, or just looking in on it, is when people are just going for each other's weak points, while brushing aside any weak points in their own case which are brought to light. If you are seriously interested in a topic, rather than in just winning an argument, the useful thing about any argument is the way it can identify your own weak points, so that you can examine them and modify your position as needed.

In a game that can be fair enough, and some discussions are essentially games, and most discussions have a games element. But when it comes to serious discussions about things that matter, playing games should be subordinated. Picking out the bits where someone on the other side has contradicted themselves, that's fun, and that's fair - but the main thing is to respond fairly to the exchanges that seem to indicate a flaw in your own argument.