I don't know about worse, but I think I can take a shot at the reason it has its own word: If I had to guess, I'd say partially because only one is equal part religion and race, same as if someone hated Muslims you'd use "Anti-Muslim" because that's the term for the religion, where as "Arabic" is a race, so that would purely be "Racism". Partially because the others didn't originate from something so internal and, thus, debated - You could hate a Saracen or a Moore in the middle ages, but that was fine because they were far away and you were often at war with them. Jews were your neighbours, had their own district, their own businesses, all in towns near by, and you weren't at war with them... But you still hated them, thus earning a special kind of attention. Same as we might identify the fracture between internal groups as "Classist", because that's where the internal divide was.

And, lastly, because, as you're insinuating, Jews work together very tightly and, because of this history of being forced to be insular, they usually come together on stuff like this pretty quickly, and in the modern world, where being the victim is being elevated, it's an easy stepping stone to get everything you want.