I need to say Romeo and Juliet is about both love and hate. Even though if from my point view love is above hate, hate is very important in the play.
To start with, on the one hand, I think love is very important because no matter what his father thought, Juliet made her marriage possible; another reason is that Romeo and Juliet died for each other, without thinking in the problems between both families. An example is when Romeo entered in the Capulet's party and kissed his daughter. On the other hand, hate is relevant too just because the families, Montagues and Capulets fought each other until they died, because their past generations were in a "war" of hatred. One example is the part in which Tybalt killed Mercutio, and because of that Romeo killed Tybalt.