I agree in principal but not in practice here.

If you’re using a typical docker host, say CoreOS, following a standard production setup, then running your app as a container on top of that (using an already hardened container that’s been audited), that whole stack has gone through a lot more review than your own custom-configured VPS. It also has several layers between the application and the host that would confine the application.

Docker would increase the attack surface, but a self-configured VPS would likely open a whole lot more windows and backdoors just by not being audited/reviewed.