You are speaking in public and someone interrupts you abruptly saying that you are wrong.
If you feel fear or anger, it's normal.
To regain control ask the person who interrupted you these questions:
Question 1: "Why do you say that?"
Question 2: "Interesting. What data are you basing it on to say I'm wrong?".
If the person's argument is sound, say this:
"Let me check what you just said and I'll get back to you. Thank you."
You have bought time to respond at another time. You've shown yourself to be open and confident. And you haven't lost control of the conversation.
Don't use your ego. Use data.