Phil Birnbaum at Sabermetric Research writes about how people have things backwards; it's great to find out that you're wrong:
Let's suppose you open a restaurant, and you're very successful, and people like your food. You're very proud of being a great chef. Then, someone tells you, correctly, that one of your appetizers, one that you think is one of your best, is actually pretty awful. Your customers hate it.
Your first reaction might be to get defensive. But, again, you should be thrilled! Now you can fix that dish. Your food, your restaurant, your profit, and your reputation will all be better than before. It's almost the best thing that can happen to you. Being wrong is like winning the lottery!
I guess my overall point is that any online discussion, even between people who violently disagree with each other, should be a co-operative venture. One of you is wrong, and you're working together to find out who. And, we should keep in mind that most of the benefit goes to the person who was actually wrong in the first place.
When someone you respect, or someone who seems to be expert and knowledgeable, starts disagreeing with you, it's like you've stumbled upon a fistful of lottery tickets. Argue your position, yes, but don't get defensive, and keep an open mind. Sure, it might be that other guy who's wrong. But if you're really, really lucky, it'll be you.