Mother Theresa was just a bit 'dim' (or just plain old fashioned) - A relative of mine knew her/worked with her - and said she was a really gentle person who only wanted to do nice things..but not too bright.
(she was old at that time)
Too me that's like saying If I organize a robbery but make sure I'm the driver I should not be held accountable as I did not break anything or steal anything.
Not true. Your is the plan to the initiation of force...(as well as abetting the initiators of force to make good from their actions of force..Complicit by action).
Mandela had no excuses - highly intelligent and as such the has to take responsibility for his actions, more than just at a 'local' level...
With higher levels of intelligence, and good intent, comes great responsibility.
If 'do no harm' doesn't run through the ethos of real life actions - at all levels - motives have to be questioned.
If 'the means justifies the end', then intellectual gymnastics takes precedent of objective moral truths - killing for example. (not incl. in self defense)
My initial take on it...
Some interesting points you raise, I'm not sure if lack of intelligence or knowledge should be seen any differently as someone knowingly doing something bad. Maybe it makes things understandable but it doesn't take away from what happened. Though I also feel if you have know knowledge of something being bad then it is unfair to punish them the same.
I think that comes down to being dependent on situation and I think in the example of Mother Teresa she full well knew the consequences of people not using contraceptives and how that can spread disease, so she should be held accountable.
I also find it difficult to say whether 'the means justifies the end' as again in some situations it will some it won't. It really is a difficult question of morality, good and bad are different from person to person. Also causing harm is something that can not be avoided someone will always be harmed to some extend in making change.
I don't like to think of people as good or bad because there is just too many arguments for and against, I prefer to look at it as people are people with individual motives, good or bad matters as much as we each make it.