It can be said that Shakespeare's theme, "religion of love," in Romeo and Juliet, makes an overall moral statement. The statement may show that the fervent, passionate, and even violent drive Romeo and Juliet felt for their love, which was influenced and enhanced by social conflicts, leads to many consequences.
For many of the play's characters, love actually becomes a religion in that it becomes many of the characters' most central belief, nature, and ultimate purpose, especially for both Romeo and Juliet. Let us look at Romeo as an example.
For Romeo, we see many instances showing that love in the form of lust is the one thought that governs his mind. we see this first with Rosaline, as he pines away all night long to take her maidenhead. Not only that, he feels that his love is killing him, which can be seen in the line, "She hath forsworn to love, and in that vow do I live dead that live to tell it now" (Act I, Scene 1). Hence, for Romeo, love instead of God or morals, has become the spiritual food that he is living on, but it is actually killing him.
The analogy between love and religion is continued when he first meets Juliet and refers to her hand as a "holy shrine" and says that in kissing her his sins are "purged" (Act I, Scene 5). But just like Rosaline, even his love for Juliet leads to his death, only this time it is literal death. While their family's hatred was the catalyst that lead to their death, it was their fervent, violent passion that was the reason for their death. Hence, one can argue that the analogy between love and religion serves to make the moral argument that this sort of uncontrolled emotion, whether it is love or hate, leads to dire consequences.