The King suddenly realizes that all that he had been seeking, after all, was not love. And now that he'd found what true love was, he could only have it by not having her.

Binnie had loved this King's dad in a way that he, as the son, had previously not understood.  And by not respecting that love, which she still clung onto so dearly in her heart, he would be robbiing her of the only love she ever knew.  No one could replace, nor could add to that love.  There is no enhancing that which is in its purest form.