The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
I am no fan at all of Michael Bloomberg, but I've got to come to his defense on this one (see here and here, giving this as an example of material that's "offensive" and "racist"). The point of the joke isn't to suggest anything bad about Jews or Puerto Ricans; rather, the humor is in the absurdity of the speaker's own implicit factual error: It's as if the speaker views Jesus Christ as being named after Hispanics named Jesus rather than vice versa.
This might be slightly insulting if the speaker is mocking others who make that error; much as "If English was good enough for Jesus, it's good enough for me" is used to mock those who are perceived as ill-educated Christian traditionalists, you can imagine the "If Jesus was a Jew" joke being used to mock ignorant anti-Semites (or perhaps anti-Puerto-Ricans). But more likely it's just absurd, and funny because of that. Nothing in it reflects any hostility on the joke-teller's part to either Jews or Puerto Ricans.
But the condemnation of the joke does reflect, I think, how knee-jerk and unreflective people have become on such matters, treating jokes about race, ethnicity, or religion as somehow per se offensive or prejudiced without seriously considering what the joke actually means.