There's a really easy trick for conceding a debate without being crowed at. The trick is to admit that you were wrong, concisely explain the change you've made to your beliefs, and warmly thank the other person for taking the time to help you become correct about this. Even if they were a bit of a dick in the debate itself. Don't declare defeat; declare a mutual victory of truth.

Anybody who can crow about your defeat after that is a huge asshole, and furthermore this should be obvious to anybody watching.

(This trick also makes you feel better about changing your mind, because you've reclassified it as a victory. I've had a much easier time conceding debates ever since I adopted this habit and mindset.)