Actually there were rallies in multiple states and in multiple countries (including Australia, the UK, France, Tunisia, Turkey, Argentina, and Brazil) in early 1933 against the already nasty persecution of Jews by the Nazis in Germany, which had begun even before Hitler yemach shemo had become Chancellor on January 30. It was mostly the thugs of the SA but in early April 1933 the Nazis were putting their evil plans into law. The big step for the Nazis was the Enabling Act of March 23, 1933, which was enacted with the positive votes of every non-socialist member of the German parliament (and opposed by every socialist member of the German parliament, most of whom would be in concentration camps, in exile, or dead within six months). The Enabling Act made Hitler a dictator with neither checks or balances other than the 85 year old feeble and nearly senile President Hindenburg, who actually hated Hitler yemach shemo. But Hindenburg died in August 1934 and the rest is history.
The largest American rally was at Madison Square Garden on March 27, 1933, four days AFTER the Enabling Act. Geatured speakers included Al Smith, former Governor of New York (Irish Catholic); William Green, President of the American Federation of Labor (Welsh); Bernard Deutsch, President of the American Jewish Congress; Reform Rabbi Stephen Wise; US Senator Robert Wagner (German Catholic); New York Mayor John Patrick O’Brien (Irish Catholic); Episcopal Bishop William Manning; Methodist Bishop Francis McConnell; and at least one other Christian minister and nine Jewish lay leaders. Governor Herbert Lehman (Jewish) had to stay in Albany on state business but addressed a large rally there. It is clear that this and other rallies were in RESPONSE to the Nazi atrocities, not a cause of them.