That you addressed your response to @DuctView with the opening "What I am saying Francis".
No one was disagreeing with your "garbage in, garbage out" stance.
After you @anav suggested putting the Mercusys on its own interface/subnet, the OP then realized there was no longer a need for the Mercusys to be a router firewall anymore, because the MT could do the firewalling and then it would be easier to allow access to devices behind the Mercusys from other allowed host/subnets on the MT. That's why I think @DuctView said "And rightly so."
DuctView was referred to as the OP in a different thread before here.