Isn't this the trusted network dialog in windows/etc when you connect to a new network?

If you don't trust the network, then the OS should be tunneling to a trusted one. If you do trust it then it can go ahead and use the DHCP/etc provided name servers.

After all it can decide to enable/disable access to services (windows filesharing for example) based on this, there isn't any reason it can't decide to trust the local nameserver too.