Saber, to be fair, has respect for Vash's ideals and the nobility of a desire to save as many people as possible. However, she still thinks it's impossible to avoid killing your enemies entirely...

... And for that matter feels there's some people so evil that the only response is to kill them. Case in point, Fate/zero Caster.

Fate/zero Caster is a [i]bastard[/i].