There are several answers with a variety of cynicism.

At the lowest level of cynicism, both parties love to have a boogeyman, and often the level of attention and criticism these targets get goes way too far.

Next level of cynicism: he’s a Jewish liberal, and a large majority of antisemities vote right, not left. By now non-racist republicans are very good at ignoring or rationalizing the bigots around them, so really loud dog whistles have no negative consequences.

Final level of cynicism: republicans and right wing parties across Europe are no longer interested in democracy, and are now trending rapidly towards open fascism. Soros’ love of free speech and fair elections are a problem to them, not a shared value between otherwise political opponents.