Joseph and Mary are walking in a cherry orchard, and Mary asks Joseph to pick her some cherries, because she’s pregnant.
Joseph gets angry, since he knows the baby isn’t his (they haven’t had sex — in most versions of the song they’re not yet married). He says to Mary, “Let the baby’s father pick the cherries for you.” (Some versions of the song call his words unkind; others say they’re angry.)
Jesus then speaks from out of Mary’s womb, and commands the cherry tree to bend down and give her cherries. Which, of course, it does.
Mary says to Joseph, “See? I have cherries at command.” (In other words: “The baby’s father is God, and I didn’t cheat on you.”)
In some versions, Joseph then begs forgiveness, says he’s not worthy, wallows in guilt, hopes God won’t smite him, etc. In other versions, Mary’s “In your face, douchebag” is left as an implication. (In some versions, Mary then asks the baby Jesus to predict the future, either after he’s born or from inside her womb — which he does. Damn, theology is weird. That’s not relevant to this particular story, though.)
Okay. So here’s the thing:
It is entirely reasonable for Joseph to be pissed.
How on Earth was Joseph supposed to know that the baby was the supernaturally-conceived son of God? Why would he imagine that, even for a second? Think of Joseph’s arc in this song. “Gee, I was such an unkind jerk for not considering the possibility that your pregnancy was supernatural, rather than the result of perfectly ordinary human sex. I mean, that’s only been the case in EVERY SINGLE PREGNANCY THROUGHOUT HISTORY.”
Assuming you accept that monogamy is a reasonable relationship arrangement (which I do, although I certainly don’t think it’s the only one), it’s reasonable to be pissed off when your partner breaks that agreement. It’s especially reasonable to be pissed off when your partner breaks their monogamy agreement, gets pregnant with someone else’s kid, and then just assumes that you’re going to parent this kid.
Okay, yes. “I’m ticked off, I don’t feel like picking cherries for you right now, let the baby’s father do that” isn’t the best response to this. It’s definitely on the sarcastic side. But as responses to “I cheated on you and got pregnant” go (which, again, is the entirely reasonable conclusion for Joseph to come to), it’s pretty mild. And Mary didn’t exactly tell him in the most sensitive way, either. “Hey Joseph, can you get me something to eat? I’m hungry — because I’m pregnant, with a baby that you know perfectly well isn’t yours. Now, make with the cherries.”
In fact, I would argue that in this story, Mary is being a total drama queen. If she can talk to the baby Jesus in her womb and get him to do telekinesis, couldn’t she have done that before this little incident? “So, Joseph, you’re probably not going to believe this, but I’m pregnant with God’s baby. I know, you have every reason to think that’s bullshit — but here, I’ll show you. Baby — bend that tree!” Instead, she manufactures this passive-aggressive little drama, where she gets to be the martyr. “Oh, Joseph, I’m so hungry, because I’m pregnant with someone else’s kid. What? You’re angry? You don’t trust that I kept our monogamy agreement? Oh, I’m so hurt. But I’ll prove it. Baby — bend that tree! See, Joseph? The baby’s father is GOD! In your face, douchebag!”