I don't know why this is said so often. Lightning is not private. Network incentives for optimal routing lead it to grow less private over time. Literal lightning devs telling you it isn't private.
bitcoinmagazine.com/technical/state-of-bitcoin-lightning-network-privacy
You're listening to a maxi who has casual knowledge of Monero explain why he thinks it's bad in a few minutes.
If you're really open to steelmanning the case at least have a Monero user there, who knows what they're talking about, to give some pushback.