"Clearly I'm interrupting; I feel badly. Let me ... what are you drinking? I'll buy y..."
"Bad? Sorry, I feel...?"
"You feel bad. Badly is an adverb, so to say you feel badly is to say that the mechanism which allows you to feel is broken."
(From the movie Kiss Kiss Bang Bang)
I'm grateful to Thomas Presskorn for bringing this scene to my attention (more here). My view is that poetry should make us feel better. I.e., better able to feel, not full of better feelings. A specific poem should make us more capable of feeling specific emotions; it should not fill us with warmer feelings about particular subjects.
This goes even for love poetry with a direct addressee. The poet is not hoping to introduce a loving feeling into the heart of the object of his or her desire. Rather, the poet is implicitly saying, "The mechanism that would otherwise allow you to feel love for me appears to be broken. Here are some exercises that might fix it." This is why a good love poem has a utility beyond what Ezra Pound called the "one obvious remedy" for the poet's unhappiness.