And I generally make it a point to take on that perspective (understand where the other is coming from) but when one piece of information comes up (ind. serv. for ex) always leading to an historically relative scenario that "one ups" the present topic at hand; in this case US black slaves, you sense a trend of where the discussion is leading and that is to divert attention from the OP instead of actually discussing it. Veering the debate to one's agenda basically. Black slaves had it terrible, BUT when you compare it to the Roman days of 2,000 years ago, etc. is just a way to avoid the topic at hand; not enhance the discussion/debate.
it can be argued that opening up the persepctive *is* enhancing the debate/discussion. also, it depends on the view of the person driving the discussion. are they trying to focus on black slavery in america or slavery through all of mankind that still exists even today in the world? nothing can ever "make it right" for the bull**** things this country has done in it's history. but these days we're literally rewriting the past as we go to cater to the mindset of today - losing all the bad *and* good from those times.
even i drifted in that simple line of thought and people will do that. drift from thought to thought. i didn't do it it minimize a thing, i just did it in the course of convo and caught myself since it was *what* we are talking about.
but to your point - if there is a personal tie to any given area that will almost always rise in significance *to you* but it still has it's place in time - to all. doesn't mean less respect or less empathy for the times - just that the other person has gone through their own set of challenges and trying to rate your views over their own - well that's where most arguments tend to get nasty. when people do it to me i tend to just walk away cause it's not worth the struggle, fight or effort.
in this case, i'm glad i we've talked as i have a better idea of what drive you behind this type of a conversation and i can certainly respect that, agree or not.