Even before the play begins, hateful language (in bold) is established by the Chorus in the prologue:
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
From forth the fatal loins of these two foes
A pair of star-cross'd lovers take their life;
Whole misadventured piteous overthrows
Do with their death bury their parents' strife.
The fearful passage of their death-mark'd love,
And the continuance of their parents' rage,
Hate is most embodied in Tybalt, who says:
After the brawl the Prince warns both families:
Romeo soon after meditates on the absurdity of the families' hate, using oxymorons:
Juliet echoes this after she finds out she's fallen for a Montague:
Romeo, in the balcony scene, hates his name:
And he foreshadows his death, which is ironically caused by love as much as hate,
Tybalt picks a fight with Romeo, thus causing his death...
...and Romeo's exile by the Prince:
Romeo again foreshadows his suicide to the Nurse and Friar Lawrence:
As if that name,
Shot from the deadly level of a gun,
Did murder her; as that name's cursed hand
Murder'd her kinsman. O, tell me, friar, tell me,
In what vile part of this anatomy
Doth my name lodge? tell me, that I may sack
The hateful mansion.
Juliet pretends to hate Romeo, but really she hates Paris and her parents' idea of arranged marriage:
When Juliet pretends to die, her mother says:
Lord Capulet follows:
Finally, the Prince echoes his earlier speech:
So, hate is the flip side of love. It's an easy word with which to rhyme. Montagues are hated. The name "Montague" is hated. Love is hated. Death is hated. Villains are hated. Exile is hated. Peace is hated. Arranged marriage is hated.
So, what have we learned? Don't hate the play-er, hate the game...