How do you explain to experts that a Database Server should not reside in the DMZ?

Our security experts, DBAs, network team and infrastructure team are all saying it's ok to have the DB server located in the DMZ along with the HTTP server and middle-ware server.

Their reason:

If the database server is compromised (because of an insecure middle tier), at least the DB server is outside the internal system. If it is inside our network, the hacker can then use the DB server to access other systems.

What they are saying is:

1. Let's not put the middle-ware server behind a 2nd firewall and the DB server behind a 3rd firewall.


2. Let's use just one firewall (the HTTP server's) in case a hacker wants to get our DB's sensitive data, at least that's all they can get.

The 2nd statement was actually said... verbatim.

Please note that this DB Server will hold sensitive information, including bank details.

Now, are these experts making any sense to you? I'm a software developer and I can't get their logic. It's like, "Put the jewelry box outside the house so that robbers won't bother getting in for the TV?"