Deconstructing the slavery pony

Where people go wrong regards two questions:
1. Are American blacks better off than the descendents of their ancestors in Africa?

This question can be answered, factually, yes.

2. Does that show that the slave trade which brought slaves from Africa to America had its good parts?

This question has no factual answer, and supplying either a "yes" or a "no" says more about the speaker than it says about the slave trade.

Here's an analogous situation.

I'm luckily unpalatable to fleas. I've never been bitten by a flea. I've had them jump on me and quickly jump off.

How could that be? My guess is that some importantly large group of people died of a flea borne disease, while my ancestor(s) who posessed the flea repellant genetic combination survived.

Am I better off being flea resistant?

Sure.

Does that mean that the death of those people had its good parts?

Well, not really.