Another very useful trick I learned for handling criticism, especially when you're standing nervously on stage and the critic is being unfriendly, unreasonable, and unlikely to change their mind about anything:

If you don't feel you can give a quick response in a way that will bring them to your side right away, instead of arguing simply keep a notepad handy and (visibly) take a quick note about what they said and thank them. Most folks that raise unreasonable criticisms at talks just want to be heard, and in my experience they may even suddenly become very friendly to you for visibly acknowledging their comments, opening the door for a productive and constructive conversation.

Everyone in the audience will recognise when someone is being a dick and will be praying for them to stop grandstanding.

“Great questions/point - would be great to pick it up with you later. Any other questions?”

I _really_ like this advice, I will be filing it away for future use. Thankyou for your suggestion :P

In my experience this goes for more than just talks - can be helpful at events and regular meetings too