In Buddhism, everything is forgivable.
If a noble person is practising their realisation, there are no grounds for us to blame them since the noble person will not be harming us.
If a noble person unintentionally harms us, they should ask for our forgiveness & we should forgive them.
If we think a person that intentionally harms us is a "noble person", we are mistaken because a noble person cannot intentionally harm others, even out of good-will (e.g., to kill a murderer) because the eightfold path prohibits all violence for any reason.
It is common for ordinary people to mistakenly believe practitioners of forms of black magic are noble people.
That is why if a monk kills any human being for any reason, including mercy killing, they are expelled from the monastic order.
AN 9.7 says:
...an arahant monk whose mental fermentations are ended, who has reached fulfillment, done the task, laid down the burden, attained the
true goal, totally destroyed the fetter of becoming, and who is
released through right gnosis, cannot possibly transgress these nine
principles.
[1] It is impossible for a monk whose mental fermentations are ended to intentionally deprive a living being of life.
[2] It is impossible for a monk whose mental fermentations are ended to take, in the manner of stealing, what is not given.
[3] It is impossible for a monk whose mental fermentations are ended to engage in sexual intercourse.
[4] It is impossible for a monk whose mental fermentations are ended to tell a conscious lie.
[5] It is impossible for a monk whose mental fermentations are ended to consume stored-up sensual things as he did before, when he was a
householder.
[6] It is impossible for a monk whose mental fermentations are ended to follow a bias based on desire.
[7] It is impossible for a monk whose mental fermentations are ended to follow a bias based on aversion.
[8] It is impossible for a monk whose mental fermentations are ended to follow a bias based on fear.
[9] It is impossible for a monk whose mental fermentations are ended to follow a bias based on delusion.