As opposed to killing a rodef? This whole thing back and forth makes no sense.
Killing a Rodef applies now like it applies when the torah was given.
Killing a Moiser applied at a time when governments authorities were likely to unjustly kill suspected criminals. The Shu"a paskens it doesn't apply nowadays.
OTOH RMF allowed sacrificing the life of a Siamese twin M'din Rodef.