In wishing to interfere with what he sees as wrong in Emma's actions, he is actually showing a similarity to Emma's desire to involve herself in others' futures. The difference (so far) is that Mr. Knightley backs off when a respected friend calls his attention to the possible results.

I wonder at his saying in ch. 5 "But I[]who have had no such charm thrown over my senses," however. The charm of loving beyond accurate memory? The charm of seeing the past only in pleasant terms? It is almost as though he were saying he does not care as much as Mrs. Weston does for Emma, when almost his every sentence in this conversation seems to show he does care.