>>The number of black people that voted for him was over 90% each election.

In recent times two white candidates, Gore and Kerry, got 95% and 93% of the black vote respectively. No doubt there is an issue of identity in black people voting for a (half) black president, but the link to party seems far more predictable.
It's also recent: it wasn't so long ago that Republican candidates (including Mitt's father George) could count on 30% or 40% of the black vote, unlike today when polls showed Mitt had 0% despite being part of a party that once had a place for the likes of Martin Luther King. That's what Republicans need to be thinking about. Seems to me that calling black people racist may provide an easy answer, but that doesn't explain the worsening results since the 1980s or provide suggestions on how to get things back the way they once were.