Wow. Just a few days ago you were arguing that LRASM is a failure. Now SM-6 too?
Being able to attack ships is one of its design objectives. The missile flies at Mach 3.5+ and plunges into the target at a steep angle, hitting the deck and probably penetrating all the way through the ship before detonating and blowing a hole through the bottom of the ship.
As to how effective an SM-6 really is:
So yes, a 4,100 ton ship can be sunk by SM-6.
Things that make you go "Hmmmmmm ..... "
Recent SINKEX, eg Both RIMPAC and the LSE ones feature target ships that survive multiple AShM (Harpoon, Exocet, NSM) each and had to be endex with a Mk48. (Survive is a loosely used term here - survive as in remain floating)
In most SINKEX case, the target ships are stripped of flammables and all hatches and compartments are sealed. As mentioned by posters, one hole ain't gonna sink a ship if damage control mitigates the flooding to just that one compartment.
The SM-6 single handedly sinking a FFG? In this case, I'd argue that all hatches were open on the FFG targeted by the SM-6 ... Brings to mind those for-visual-effect ATGM demos where they fill the target AFV with flammables and HiEx.
I'm not arguing that a SM-6 cannot be used as an AShM. It has been demonstrated that the capability exists and works. Just the David v Goliath image of a 64kg warhead doing what it claims to have done. As to the arguments of value of a $5m missile being used in this role. Hey, in war, you throw whatever you have at the OPFOR. If a salvo of SM-6 can mission kill a combatant it's good value.