Why is Romeo unafraid of Juliet's kinsmen?

In Act II, Scene 2, of Romeo and Juliet, Romeo, overcome by his immediate attraction to Juliet at the party, decides to go over the wall onto Capulet's estate to see if he can see Juliet again. After some memorably poetic lines between the two—"Romeo, Romeo, wherefore art thou..."—Juliet pleads with Romeo to leave the grounds before any of her family sees him:


How camest thou hither, tell me, and wherefore?The orchard walls are high and hard to climb,And the place death, considering who thou art,If any of my kinsmen find thee here.



It's really not so much that Romeo is unafraid of Juliet's kinsmen, rather he is afraid that the girl does not share his affection:



Alack, there lies more peril in thine eyeThan twenty of their swords. Look thou but sweet,And I am proof against their enmity.





In other words, if Juliet does not like him, the swords of her kinsmen are not as harmful to him as her rejection. Moreover, Romeo claims that they will never see him in the dark and, in any event, he would rather die at their hands if Juliet's love was out of reach:



I have night’s cloak to hide me from their eyes,And, but thou love me, let them find me here.My life were better ended by their hateThan death proroguèd, wanting of thy love.





Here, for one of the first times in the play, either Romeo or Juliet threatens death in regard to the young lovers' relationship. In Act II, Scene 6, Romeo says he would just as soon die after he and Juliet are married:



Then love-devouring death do what he dare,It is enough I may but call her mine.





Romeo again threatens to kill himself after the slaughter in Act III, Scene 1. Likewise, Juliet carries a dagger with her when she consults Friar Laurence after hearing that her father has betrothed her to Count Paris. These remarks foreshadow the eventual double suicide in Act V.