Dzhokhar is a terrorist that has shown no remorse for his actions. Not only is it offensive to keep him alive with taxpayer money, but it is also senseless. The punishment must fit the crime, and Dzhokar deserves to die.
Dzhokhar played a secondary role to his violent and authoritative brother. While there's no doubt he committed a heinous crime, putting him on death row accomplishes nothing, especially with the moratorium currently in effect that means he's unlikely to actually be executed anytime soon.
Capital punishment is a barbaric affair that compounds violence with violence. It eliminates any possibility of rehabilitation, drains tax dollars, and forces the victim's loved ones to relive the crime. The death penalty is no more effective at ensuring a safe society than a life sentence - we need to reform our sense of "justice".