They are saying exactly what I have been saying: a national leader should not, must not, "otherize" groups of people. Germany in the 20's and 30's was suffering through the humiliating conditions of the WWI peace treaty. And suffering the ravages of the Great Depression. Antisemitism was not new, it had reached a fever pitch in 19th and 20th century Europe. And Hitler focused the disaffected elements of German society on the handiest scapegoat available: Jews. In fairness to the German people, few even knew the Final Solution was in progress.
Now, as to America under Trump, people like the members of Never Again Action simply recognize that Trump has created an "other", "scapegoats". I do not imagine for one minute that America will open death camps for Hispanics. But, Never Again Action recognizes that one must nip "otherizing" in the bud. If not, incidents like the El Paso massacre become possible.