The King will be suspicious with the cagey-ness of Merlin's responses, but overall, not react super negatively. He seems to understand Merlin's stance on either withholding the information and/or not knowing the answers, and so he responds:

"Every good general has a backup plan," King Ka'pouli tells him, his tone tight, almost reluctant to admit such a thing to a stranger. "My people must survive, one way or another. A safe haven is a safe haven, regardless of what it is. And if the false Queen insists on killing us all, then I must do what is best by my people."

(And no worries, Merlin -- not yet!)