All depends, there's the term castle catholic in Ireland, though the equalisation of poverty has made that pretty redundant now. Like I said this shows that racism is always tied to class, once there are more and more black middle and upper class then I imagine terms like Uncle Tom will fade away, just as the Italians, Irish and Jews all went from being "racial" groups to becoming white in the US. Not sure what terms there were for members of those groups who assimilated into the middle and upper classes in those days but I'm sure there were equivalents to coconut, actually Ham on Rye is the jewish equivalent to coconut or uncle tom.
As for it going unchallenged, well I'm not going to have a go at anyone calling Rice an Uncle Tom, I don't think the ex US secretary of state needs my support, being the US secretary of state is much more demonstrative of privilege. Sure there are issues to be raised about why someone would expect some sort of racial solidarity of black or asian people that they don't off white people but that is a whole other issue regarding oppositional identities etc
eta actually as butcher's points out terms like uncle tom and coconut work in place of a class anyalsis or more accurately racialise class.