His comments are basically not about Coinbase itself, but rather companies like Coinbase that centralize keys. (e.g. almost every exchange, companies like Circle, lots of user-friendly wallets)

He mentions a number of things as to why
"US banning bitcoin and seizing Coinbase funds. I think this one is in the realm of 'not-gonna-happen'. Or perhaps more accurately 'if it happens, bitcoin is doomed anyway'."

I think people don't understand what a ban in the US would do. First of all, all 'public bitcoin activity' is out on day 1. That means banks won't service you, no ATMs, no deposits at exchanges, no payment processors like Bitpay or Coinbase. It means merchants will walk away and it means all VC investments leave.

It also means bitcoin drops to a near worthless price within hours. Miners stop mining, the network security breaks down and it becomes easy to do 51% attacks on the network. Trust is completely lost. Price volatility skyrockets. Most exchanges are effectively rendered unusable and shut down (example in China). You can trade on localbitcoins.com, but you never know if you're trading with an FBI agent.

There is no reputation or trust anymore. Bitcoin can still be used, but there's no point anymore. Because it's illegal, it's now risky, expensive, there is lots of friction in the system. It's no longer a better currency, and virtually nobody wants it and you can't find anywhere to spend it. Even on places like Silk Road, you don't know if you're buying from an FBI agent when you give them your address to have illicit goods, or hell, even completely licit goods (purchased with illegal bitcoins) sent to you.

In other words, this idea that bitcoin is made illegal in the US or bitcoin companies start to get shut down because they use bitcoin is not a reason for me to manage my own keys because in such a scenario, I wouldn't even want or care for bitcoin private keys any more than the least accepted unknown shitty altcoin there is.