That happens in the US and nobody cares, you could argue that it would be more powerful in europe but I don't know if that's comforting since it might mean the europeans would be more accepting of anti-semitism.It doesn't eliminate antisemitism. But it does help ensure that the historical consequences of antisemitism are preserved and taught.
Imagine if antisemitists could openly say that the holocaust is a Jewish conspiracy? It just plays into the image of the Jews as a NWO that controls everything.
Hate speech has been clearly visible well before Trump and will be after. These laws I think in theory might work only when the society generally frowns upon whatever the specific "hate speech" is already. That's why arguing for laws banning Trump or his speech are silly. Would Marco Rubio's justice department enforce those laws? Maybe he could get away with banning the KKK, but you can't ban the Tea Party and the Tea Party can function quite well without being explicitly racist, much like any european party could. The argument generally seems to be that well, countries with these laws decided a long time ago at a point in time when very few people were prejudiced that these laws were a good idea, and the people with the right morals will have control forever.Of course the laws work. It's not legal for you to run blatantly racist rally's How often do of such rallies occuring in Europe, and of course when they do happen they generally get broken up by the police because that's their purpose.
Compare that to a presidential canitate who is inciting racial violence and routinely has such violence occurring at his rallies.
This is quite litterally the worst time to make such arguements when America litterally has president candiate that has run his campaign based on hate speech and it's visible to see all the problems that entails.