Hungarian national mysticism, mostly built around the idea of that the Magyars did even less crimes in history than we often dare to admit.

Since a big issue was the genocide of pagans by Stephen I. (to the point barely anything remained of it), a large chunk of it is to rewrite the religion part of our history. Even crazier is that many of them assume we were the Huns too, and since there was some myth that Mary might have been a Hun princess, this also proves Jesus Christ was Magyar himself. It is often paired with the idea that the idea, that the Carpathians are "actually the ancient home of the Magyars, because Huns", thus denying the genocide of Avars, displacement of Slavs (this is very important, since Slovakia's territory used to be part of Hungary, and denying the legitimacy of a nation is a good gateway for ethnic cleansing á la Russia), etc.

Looking at historic facts and evidence selectively, misinterpreting them, ignoring anything that contradicts them. Also, just making shit up and saying it with a straight face so you don't question them. It also helps that the time period isn't well documented so they can just fill the gaps with fantasy.

If you don't know much about history and don't look into their claims at all they can be surprisingly convincing.