He's pointing out a conflict of interests. The Judge is a member of La Raza. A Latino advocacy and aid organization.
Actually and aptly enough, La Raza was founded in response to the stereotyping of people with Spanish surnames, according to immediate past president, Joe Murillo.
"There were judges on the bench saying people with Spanish surnames were prone to be savages," Murillo said. "When we tried to integrate with the mainstream bar association, we were denied. We were marginalized. The only people who were willing to work with us were us."
In 2004 a Politifact Nexis database search turned up the group issued a strong letter at that time calling for the ending of an LA show that had illegals competing for the services of a lawyer and a green card. Their complaint?
"[The show] functions as a magnet to encourage people to enter this country without documentation.
The bylaws indicate the group is concerned with:
"The purpose and goal of this association is to promote the interests of the Latino communities throughout the state and the professional interests of the membership."
It's membership, according to Murillo, is about half Latino. The conservative Red State called Trump's attempt to dishonest and noted that the attempt by Trump is to associate Curiel with the radical left wing and immigration driven group, the National Council of La Raza, with which the jurist has no association instead of La Raza, which is essentially the Latino bar of California.
He's a member of La Raza.
Which isn't a Mexican organization.