Well, Hass, I think it's okay to deliver intelligent criticism of the aspects of a particular culture held by people of X ethnicity (or religion), but one must tread very, very carefully-- cause it's a real fine line between that and racism. For example, when right-wing racists use completely legit criticism of some negative aspects of Black culture from people like Bill Cosby. Which is why I generally think it best to leave such criticism up to those from that group, and if I hear it coming from outside the group, my radar is up and I'm gonna pay very close attention to where they're going with it-- if it's really a legit, non-bigoted criticism or just clever justification of racist/bigoted/discriminatory views or policies.
Of course religion and ethnicity, while sharing some commonalities, also have a distinct difference in that it's a different matter to criticize someone's beliefs than to criticize someone's skin color or whatever, even though care must still be paid in the former case, because, more often than not, just as in the latter, it's something someone is born into. Furthermore although I can see justification for attacking religion like any other belief system, I see no justification for attacking ethnicity as it's not a belief system, and, as you say, it would make just as much sense to attack someone for their height.
So that is my rambling only somewhat cogent response to your question.
To put it in simpler terms-- those criticizing religion may be either bigots or principled people, but those criticizing ethnicity are almost always bigoted pieces of shit.