History is a journey. We would not be where we are today but for those who came before. Were we born into their time and place, we would have been viewed just as reprehensibly as those who came before. We should be grateful for those whose part in the journey is worthy of some respect even if all of their beliefs, actions, and efforts might not be viewed today as such.
To me this whole "respect history" is not carte blanche for truly evil men. It would be an interesting exercise to attempt to define by what rules this exception should be invoked. I read a book last year that completely refuted the rewrite of history that Hitler's Reich was imposed on an unwilling Germany. From original sources he shows it was not so. Even a cultured, respectable society is capable of being led down a bitter path. Clearly Hitler is not to be honored. But...BUT, many people who, were we to know them, we would think noble and honorable either supported or acquiesced to the Nazi state. It is a sobering truth that, were we born into Nazi Germany, we likely would be just like them.
I say it again. By the measure with which you judge, you will be judged. You are not only a current judge over men from history, you are yet to be in the dock and subject to the judgments of men in the future. If you now deny men any sense of fairness to the time and place of their birth, consider whether you might feel differently if such a fairness were denied to you.