This is true online and it's true in person. As you said even if you "win" by getting the other person to concede, the net result is often that they are more walled into their position than before.

I've come to believe the real issue is that you should not be trying to "win" a discussion in the first place.

Rather, you should assume (or at the very least pretend) for the moment that their position is justified and they are "right". Under that presumption, ask questions and allow them to elaborate on their position. In short, instead of talking, listen without judging until you really, truly understand and have acknowledged and accepted their position.

At that point you have a tool very few people ever acquire in a discussion. You have the ability to frame your argument in their terms.

Now, that doesn't mean you will convince them you are right and they are wrong, but it does mean they are going to be far more likely to listen to you and consider what you've said more fairly than if you had simply bombarded them with facts and figures, i.e. "logic".