I know they are all against Jews, but why?

this isn't even correct.

Anti-zionism is opposition to the creation or continuation to the modern state of Israel.

Anti-semitism is hatred of people of Jewish descent.

Anti-judaism (I've not really seen this term used) would be opposition to the religion of Judaism.

Anti-semitism is essentially racism against people with a Jewish heritage- not exactly racism since, ethnically speaking, Jews are not a distinct population, and anti-semitism focuses on the religious and cultural differences between Jews and non-Jews. At any rate anti-semitism is never justifiable and in some european countries is explicitly illegal due to the heritage of WW2 and the holocaust.

anti-zionism is opposition to the creation/existence of the state of Israel.