Earlier quoted context omitted.
Hitler was elected based on the premise that he would save the German people from destruction, the exact justification you excuse, not simply because he hated Jews.
and making it illegal for parties to call for genocide would've helped his campaign, how? It doesn't necessarily harm his campaign as he could/did just dogwhistle instead, but it certainly wouldn't help it. FWIW Hitler wasn't the example I was thinking of when using that example. He didn't AFAIK explicitly call for genocide but he did dehumanise Jewish people with propaganda.
You know... Exactly what actually happened.