I graduated college in 1979, and even by then it was clear that wearing blackface or Klan garb was NOT funny, but offensive, and not just in the north. Although many have raised the point, with which I generally agree, that one should not be held to the standards of today for past bad behavior. If so, no one would run for office -- we all have skeletons. And it is politics, where mud-slinging is an honored tradition.
But this is a rare case, in which the actions of a young man should make us wary of his judgement later in life. There seems to be no doubt as to him doing this. And no one called him out on it because, oh, we were all drunk, young, and clueless.
But by then, there was enough obvious controversy that it's hard to believe a smart med school student would be unaware enough to do it twice.
The sixties and seventies turned everything upside down. Despite that, there were many cases of poor judgement on the issue of race:
Joni Mitchell, of all people, went to a party in blackface in 1974. And she was not widely criticized, despite that her next album cover featured a photo of her in this same costume.
But there were many who realized the insult of blackface, including this 1977 decision by U.S. Postal Service, surprising to us New Yorkers as the complaints were in "several southeastern states":
"Controversial Poster removed by Postal Service"
If you need a subscription to read this article, here's the guts of it:
He can start here:
A very good report on the history of blackface (make sure you watch the video)
and then to bring him up to date: