Stable coins fail when there's a run on the bank. Crypto is a wild west of unregulated banking. They have essentially become tools for money laundering and scam enablers, so it might take a while. But eventually the general public will say "no thanks" to a pain in the ass version of regular money. When the rush to the exits happen, the ~7 txn/s limit of Bitcoin will become painful.
What in the world are you talking about? What stablecoins are you talking about operating at 7tx/s? Why do stablecoins fail when there's a 'run on the bank'? You're mixing so many metaphors here that I'm not sure you know what you're talking about at all. This is a stablecoin: https://en.wikipedia.org/wiki/Dai_(cryptocurrency). If it isn't permissionless it's not a 'stablecoin' it's an IOU.
Without commenting on the rest of either of your posts, he is talking about how to trade between stable and other coins with that limit on Bitcoin. i.e. He is saying there will be so many people trading away stable coins for Bitcoins (as in Bitcoins not generic stand in for cryptocoin) or other coins that the 7tx/s limit of Bitcoin wallet transfers that it will become a significant factor as Bitcoin is used as a 'reserve currency' for these trades.
