Some very fair points here, but I do have two misgivings.
First, there's the issue of arrogance or at least excessive self-confidence (and I am referring here to our entire approach to the past, not to you specifically - none of this is personal!).
If the people of the year 2300 judge *us* in retrospect to be wickedly immoral, will they be right?
I don't have a problem with saying people in the past did things that were wrong. Clearly some did - whatever the criteria for badness, there were surely bad people then just as there are bad people now.
I'm a little sceptical, though, of our confidence in believing that *we* know definitively what's right.
It's perfectly natural to believe that, of course, but if we're going to really think about these issues, we have to at least acknowledge the possibility that *we* are mistaken about right and wrong. (This is leaving aside, of course, the question of whether absolute, context-independent rights and wrongs exist anyway.)
Then, there is the issue of responsibility, or intention.
Even if we *have* discovered the ultimate truth about right and wrong, we have to consider the very strong possibility that people in the past didn't have access to that truth.
If somebody in the year 1500 did something which was indeed evil, but *did not know it was evil*, can we condemn them in the same way we would condemn somebody who knowingly performed an evil act today?