Never really understood the goal of Ethereum or why does it exist and in what basis does it do something that is better than Bitcoin or that Bitcoin isn't capable of doing, or if it has something that drastically improves the usability of the blockchain and monetary tokens. Not really getting why there was a fork either (someone trying to control most of the hashrate, as far as I understood...?)
Despite this, I don't think Ethereum is a good benchmark for evaluating dangers and advantages of hard forking Bitcoin. Bitcoin is more widely known and accepted. I think we can call it the king of cryptocurrencies. You can fork all the altcoins you want. You'd probably only be able to benchmark possible problems in forking when forking Litecoin, and even so...
They forked because the dao was "hacked" and the "hacker" would have had a shit load of eth once he finally got his tokens released which he would then go ahead and dump no on the market which would collapse eths price.
I can't see coinbase ever admit they where wrong though. If anything this shows hard forks should be approached with caution even if i do support bigger blocks.
They'll reach out and be like "Oh yeah this is all great and cool and you know we like this too so check us out" so they can kiss the users' asses for their revenue. I changed wallet sites for a reason.