Nothing wrong with disagreeing with him on that one. Firstly because we don't have many jobs that can can naturally be pushed into the tank role (the whole thing with DRK easily showed this). Secondly, a guy in lamellar armor (which is what samurai wore) not taking hits is just silly. Sure, lamellar armor can't take the same type of hits as well as plate armor can, but it wouldn't be unreasonable for SAM to have a mitigation mechanic to still bring them up to par with WAR and PLD.
I could be convinced to accept SAM as a DPS, but they'd have to pretty much look like
this instead of
this.