I'm an unwavering opponent against the death penalty, but with that said, I can perfectly understand the thought process of one who feels, at his/her core, that Tsarnaev doesn't deserve to live. It is a mentality purely driven by reactionary emotions, and there's nothing wrong with that; it's human to believe his penance should be the equivalent of what he committed. "Why do I have to pay my hard-earned taxdollars to keep sub-human filth alive?" It's inane to call people 'inhumane' for responding to a circumstance like this, let alone calling them 'no better a person than the killer itself' - what the fuck is this and what sort of grotesque mental gymnastics does one have to perform to reach this conclusion?.
But evaluating the situation with complete neutrality - the death penalty is never acceptable. Ever. Let the trash rot in jail where he spends decades upon decades staring at a blank wall. If we're talking purely punishment-wise, that's perfectly viable. Additionally, it's a non-barbaric, non-violent resolution that, while allowing leeway for rehabilitation/remorse (if possible), is also economically more viable than capital punishment.