So you continue to dodge. This is embarrassing too, of course, but we know people have a preference to stick with a lousy status quo rather than move to a lousy alternative.
What to do? Just say yes. It may feel embarrassing at first, but it's actually admirable for someone to admit he was wrong. It's actually good to learn new things. Sure, some might gloat, but in the end, they're forced to respect your honesty and reasonableness. As opposed to what's happening now, where this is just a joke that's getting less and less funny.