Both words were made by the same people, claiming a racial difference between those descending from semitic cultures and those who were not (this was already debunked by the 1920s). "Semitism" was intended as a pejorative, with "Antisemitism" being the idea of "cleansing" the society from the negative influence of "semitism".

It's a made up Boogeyman used as an excuse to have something to push back against... and of course you can unite people around those ideas.

As a freakishly recent example, right now I've been watching the news on TV here in Spain. There is a problem around choosing a president, with the opposition using every strategy they can to discredit the incumbent.

One of the arguments they just decided to get up in arms about, is the incumbent just revealed agreed to forgive 15B€ of fiscal debt from one of the regions, which the representative of another region was being shown Live heavily criticizing, going on about how it should be all regions negotiating together, yadda yadda... and just then a news ticker goes by, stating that the incumbent has also agreed to forgive another 12B€ to the region of the guy just speaking Live. So much for "negotiating all together"!

Boogeyman created, and debunked Live. Wish I had recorded it. 😄

But wait, there's more!

Just then, they switched to the speaker for the opposition party, also Live, who started criticizing the incumbent for trying to agree on which days are going to be holidays and which work days, to fit in the voting calendar... news ticker goes by: opposition party, with majority in the Senate, tries to urgently pass a law change to delay the votes so they fall on holidays and the incumbent runs out of time.

Seriously!? Two in the span of less than 10 minutes! 🔔🔔