Ship tracks are concentrated to an from that continent. So the effect of the clearing of those tracks was concentrated on those oceans. The fact that they could warm more easily than expected, only mattered when they started to warm. And then a sufficient area warmed sufficiently quickly to impact global ocean temperatures.
That's the problem with snarky dismissals like the one that you just gave. Often they are missing some important point that will move the think you are ridiculing from ridiculous, to surprisingly reasonable. And if that happens, you're the one who looks bad.
As an alternative, I would suggest curiosity questions. If there is no good answer, your point is still made. And if there is one, you will still look good. The only disadvantage is that you don't get the pleasure of that "gotcha" moment.
