If she took such a step as torturing an enemy-affiliated civilian to death, I doubt Dumbledore would lie and say he did it merely to give her political protection in a very improbable future where Voldemort was defeated but Lucius Malfoy retained great political power.
He’s giving her political protection because he needed her during the war, and needs her now. He doesn’t want to weaken his army. Now, the same applies, with the incentive to cover his complicity.
As for what Dumbledore said, he said it to Malfoy, who was not going to be believed by others. Even if it wasn’t true, it served his war aims to have Malfoy believe he was ruthless enough to do it.
He’s giving her political protection because he needed her during the war, and needs her now. He doesn’t want to weaken his army. Now, the same applies, with the incentive to cover his complicity.
As for what Dumbledore said, he said it to Malfoy, who was not going to be believed by others. Even if it wasn’t true, it served his war aims to have Malfoy believe he was ruthless enough to do it.