This painting is the climax of the feud between Caravaggio and Giovanni Baglione, the 17th century Italian Mean Girls.  

Baglione comes in, new artist on the block, and learns how to be a cool, popular artist by wearing pink. I mean, by adopting Caravaggio's style.  Caravaggio freaks that Baglione is going to try to usurp his popularity, and Baglione is like “Um, well, I never liked you anyway because you’re a bad person!” (Which you can decide for yourself by reading about  Caravaggio's antics.)

Basically, after the two started to have issues, Baglione was commissioned to do a painting similar to Caravaggio’s Amor Vincit Omnia ('Love Conquers All'), and Bags took the opportunity to be rude as hell.  In Sacred Love and Profane Love, a winged creature comes to break up what seems to be a sexual encounter between Cupid and the devil.  This Cupid looks like the one Caravaggio painted, a likeness of his favorite model Cecco Boneri, and the devil looks like Caravaggio.  So a few things are happening here:

First of all, taking his cue from an 8th grade boy playing Counter-Strike, Baglione is insulting Caravaggio by calling him gay.  Secondly, the hero, “Sacred Love”, is punching Cupid in the face to stop the act of sodomy.  Cupid!  You know, like the baby?  So maybe before he got all “holier than thou” about homosexuality, Baglione should have gone lighter on the baby-punching.

The two paintings were commissioned by brothers and now hang side by side, which I’m sure the enemy artists would have loved.