The whole conceit of this conversation is that iforgotpassword has (a thought experiment of) a router where they've managed to "turn off the firewall" but still expect safety due to the use of NAT. My comment was about how that is not true. ie a) if it's easy to turn off the firewall then it's also equivalently easy to turn the router into a bridge, and b) if there is no firewall then bogons on the WAN will not be filtered and will instead be forwarded to the LAN.