My position has always been that Janeway has an obligation to the lives of her crew, and to do what's best for the ship. It's not a question of whether it's "right" based on human rights moralities, but whether it's to the benefit of the ship.
And how the fuck is killing Tuvix best for the crew?
And don't give me the its good for morale bullshit. You don't just murder someone becuase people don't like them its immoral and makes the crew of Voyager look like monsters.