Being wrong is the best possible outcome of an argument, as it's the one with the highest expected knowledge gain
No, that's backwards. Learning that you are wrong is good if and only if you are wrong. But it's only good because you were already wrong, which was bad - you were making bad decisions before. It's like saying that it is better to win the lottery than to be born rich. Roughly speaking, it doesn't matter when or where the money or knowledge comes from, only that you can use it.
It isn't that winning the lottery is better than being born rich, it's that winning the lottery is better than not winning the lottery. Even if you're already rich, winning the lottery is good. Presumably you weren't born right about everything, which means it's more useful to lose arguments than win them. After all, if you never lose an argument, what's more likely: that you are right about everything, that you're the best arguer ever, or that you simply don't argue things you're wrong about?
A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).