Coinbase like to ban accounts without reasons. People say the same about paypal. And despite of it, a lot of people are going to buy crypto there and after it we will see much more threads like this
The problem is that any ban should mean they will not provide any exchange services to you but should allow you to withdraw or at the very least send coins to an address they came from. That second option would suck for people who used coinbase address to withdraw from other services like online gambling sites but would be at least partially fair.
Stealing client funds is never the right way. I stopped using them a while ago after reading of people who had similar beefs with them.