Until you can verify Coinbase's internal security and practices, trust every employee with access to your account info, and verify their honest intentions, it's still pretty much a "random website". Until then, you're effectively driving your Ferrari across the border into Tijuana and tossing the keys to a random barkeep.
When comparing to established financial institutions and systems, I think it's fair to refer to even the most reputable BitCoin service provider as a 'random website'. That's the point that's being made.
Yes, please get back to us when you have verifiable proof of their security. This is Bitcoin we're talking about. It doesn't matter how "reputable" they appear to be.