What's absurd is your ridiculously spurious comparison and false equivalency.  Please enlighten us to what name a white person could be called that would equal this 'friendly' joke.  It boggles the mind that someone as learned as Dr. Marrus would not realise that singling out a racialised/marginalised member at his table for a racial 'joke' was not just inappropriate, it was unkind.  What this illustrates is that despite the long history/existence of black/brown people in this country, there is still (wilful) ignorance of them, their experiences, their history; to know nothing other than stereotypes on television, shootings, and police brutality.  How, pray tell, is that possible?

BTW a resignation is over the top.  A simple public/private apology is more reasonable.  This could have been a teaching moment for him and others like him.  The person to whom the comment was directed could have been more charitable and accept it. Who knows what kind of friendship might have been forged.