Do anti-Semites actually believe what they say?

Every time anti-Semites(and many other non-Jews) talk about Judaism it’s abundantly clear they have no idea what they’re talking about and are just repeating what others made up, and yet they don’t realize it? How can this possibly be? Surely they don’t act like this when it comes to other groups, but somehow when it comes to Jews they just take everything they hear from other non-Jews as fact and refuse to ask actual Jews? It was slightly(VERY SLIGHTLY) understandable hundreds of years ago, but there’s no excuse when we have Google. I cannot believe that these people actually think they know our religion better than us.