I am sure coinbase / gdax wants to maintain the position as most trusted cryptonvendor in USA and will find a resolution for this issue. Otherwise I imagine the below is an easy start to arbitration/lawsuit which will cost way more money and time to resolve than it’s worth to make everyone scraped on this endeavor vs hurt really badly.
Coinbase/gdax had lack of controls in place to facilitate a appropriate vetting process for margin activation.
Coinbase / gdax had lack of appropriate safety measures to protect un educated investors from the risk of loss.
Coinbase/gdax did not exercise caution in protecting its customer base from risk.
Coinbase/gdax did not have a sufficient notification to warn customers for activate margin trading on there platform and just enabled it based on an automated qualifying criteria.
Coinbase/gdax demonstrated lack of ability to handle volume and shortcut Ted qualifying process as evidence of May of 2017 signing on 40k members and acknowledging lack of support staff to even respond to complaints. Hence gross negligence.
And I wrote this on an iPhone. Your client base effected by gdax/coinbase negligence is very modivated and has the means to make it an expensive resolution. Just make is easier on everyone and come up with a fair equitable resolution.