Personally, I do in fact believe that Romeo's Punishment was fair. Not only because he killed another man, but also because instead of "facing the music" per say; he ran away from where he killed Tybolt. If anything, Romeo got incredibly lucky; thanks to his father Romeo's sentence was reduced from immediate death, to just banishment. Its understandable that Romeo had a clear motive to have killed Tybolt- but was taking another's life worth avenging his best friend? That's a question, left to Society's standards and that persons morals.