Is it because he's the voice of reason?

Or could it be he wasn't afraid to contradict Lord Trump?

Maybe its just because the Liberals like him?

Or is it simply because, rightly or wrongly, his positions and opinions are based on his qualified scientific assessment, not on ideology or politics?

Right wing hatred locks on to certain personalities like a heat-seeking missile. Persuasive voices, particularly those supported by long experience or training, or academic credentials, are especially hated by the Right. Bernie Sanders is a declared Socialist, yet he doesn't get as much flack from the Conservatives as does Dr Fauci. They expect Bernie to oppose them, but his opinions can be dismissed as opinions. Fauci has a great deal of experience in the field of fighting epidemics, under both Republican and Democratic administrations. This makes him particularly dangerous. People might listen to him.

I suspect Anthony Fauci (as well as Hillary Clinton and Nancy Pelosi) will be in prison if there's a GOP victory in the next election.