So what does one respond to this?
I know what. Calmly walk away.
You, Sir, clearly know a lot more about all these things than any of us. I'm sure you have been heard as an expert on these topics in court and have given dozens of keynotes about this at various conferences over the past two decades. I'm certain that you have been close friends with many of the key developers of open source software since the 90s (including those filing these fun lawsuits), were in the room when the term "open source" was coined, and have considered Linus your best friend for more than two decades; certainly you have had his daughters over to babysit your daughters many times, work out with his wife a couple of times a week and are looking forward to your next dive trip with him in a couple of weeks before you are on stage with him again for another fun little keynote.
I applaud your employer for their brilliant choice in expert and will withdraw from further participation in this argument.
The stage is yours. Enlighten your curious audience.