Ha! The Graham worship is pretty amusing.
Spare the rod, spoil the child. Everybody else but Yes Man is quite easily murdered. Why should Graham be super special? Just because one loves the Legion? I love House, but that doesn't mean my cannibal character didn't slaughter and devour him. A player's judgement should be what decides who lives and who dies in a Fallout game. Killing Graham is fairly lame, just like killing Old Lady Gibson is fairly lame. Not because Josh is glorious and powerful, but because he's a good guy who doesn't really deserve the Courier's enmity, just like Gibson's a nice old lady whose only "crime" is having a powerful, unique shotgun on her person.