Of course you don't want to isolate limpers OOP with weak hands. But now that we've done it, we're going to shut down at the first sign of an ace?

I agree Ax is in Villain's range, but since he appears weak passive (having simply limped in and called a pre-flop raise), I suspect Kx, Jx, 4x, and even something like Qx may also be in his range. So can any 2 spades or any 2 diamonds. And we've sat there representing AK all along, on a board that now has an ace and a king on it.

Yes, you can c/f, but I'm not sure we don't have some fold equity here.