Yes we could have said NO to a slave trade that had gone on for centuries. But we did the next best thing - when the better angels of our culture took over we ended slavery here - then we went to that hellhole in Africa that was running the slave trade and we put an end to them too.
So yeah, we should have done it sooner. The slave trade was evil - but it was blacks who did it and who did it for hundreds of years. Black Americans need to get real about their historic victim-hood - and lay a little blame where it belongs.