On a day in which Donald Trump gained the stamp of approval of House Speaker Paul Ryan, he added to another dark chapter of his candidacy by upping his attacks on the heritage of a judge in a case involving Trump University.

Specifically, Trump told the Wall Street Journal that U.S. District Judge Gonzalo Curiel had an "absolute conflict" overseeing the case because of his "Mexican heritage" and his membership to a Latino lawyers' association.

Curiel was born in Indiana to Mexican parents. "I'm building a wall," Trump said. "It's an inherent conflict of interest."

Putting aside the fact that Trump's position that a judge of Latino descent would be inherently biased against him is at odds with his campaign boasts that Latinos love him and will vote for him in droves, it gives lie to the idea that his position on immigration is rooted in wanting to prevent illegal entry and criminal acts.

In this case, Trump can't hide behind the excuse that he's attacking an immigrant who snuck into this country illegally to push drugs and commit violence. In reality, he is attacking somebody who was born and raised in the heartland of America, and who as a prosecutor actually helped take down a leading Mexican drug cartel.

But to Trump, he can do nothing to wash off the taint of his parents having been immigrants. If Curiel is ruled out of bounds because his parents happened to have been from Mexico, then it's unclear where Trump's disgusting bigotry can end.

As an American Jew, I'm certainly familiar with the age old dual-loyalty smear. Though American Jews are supposed to somehow feel safe in Trump's America, reassured as if Ivanka Trump were a modern day Queen Esther, Trump could just as easily be arguing that a Jewish judge is against him because he refuses to be beholden to Jewish donors. Or an American Asian judge is against him because he wants to get tough on China. Or an Irish Catholic judge is against him because of his attacks on Pope Francis. Effectively, anybody who isn't a white Protestant of European ancestry can be a target of Trump's ethnic and racial attacks.

This stuff stopped being funny a long time ago.

But what's incredibly scary is that Trump has not only won the Republican nomination, but that leaders who should know better have fallen in line behind him.

We're told that leaders like Ryan and Sen. Marco Rubio simply have to fall in line behind Trump because they're Republicans, and that they don't have to endorse everything he says.

That is simply not enough. Ryan, specifically, has for years earnestly talked about the American Idea. Well, it's hard to think of anything more antithetical to the American Idea than the view that a child of immigrant parents who rises to become a federal judge cannot stand in judgment of a white American of European ancestry purely because of his parent's national origins.

Every Republican who endorses Trump has hate on their hands.