A child abuser can be condemned. Could do it another child abuser? Yes, but has the Morals to do it? Of course, not.
Same logic can be applied in similar situations.
Can anyone condemn historic characters for actions made in the past, that today are considered crimes and morally unacceptable?
Anyone can condemn but has not the Morals to do it.
The only way to have the Morals is to demonstrate that under same historic conditions he/she would have considered those actions morally unacceptable. If he/she can prove, the Morals stand on your site. If he/she cannot all remains is to right to condemn.
There is a second moment. Most of those characters stood out amongst their peers, who had the same historic opportunities to stand out…but did not
Modern Accuser, can you stand out amongst your peers nowadays?
If you do not, lack of Morals get highlighted.