If every politician with a purported racist leaning had to resign, there would be a mass exodus right now across the country.
I think the more fascinating part of the story is that he really can't resign because he has no where to go. He has been blacklisted (so to speak) from ever working for a Democratic/liberal group again, and I'm not sure a medical practice group would be interested in him either. The Left does not offer redemption to someone who they think is a racist. He is done.
I was just in the same town where he grew up -- Nassawadox on the Eastern Shore. They are Republicans. He won't receive a parade to say the least.