well I guess he means that Nazis are like cultist or rather any zealots of any religion in a sense that they are blindly following some ideology made up by some guy and that he therefore neither likes religions nor nazism. To saying Lemmy would "sympathize" with Nazism is just plain wrong. Of course he did have a rather weird hobby...

Brain rot

To the point, ideology is, to a degree, a modern equivalent of religion. It provides a framework to view history and the future, dos and don’t, utopia to strive for, often comes with own set of (almost)religious practices and idolization. It even requires a degree of faith in utopia being achievable. I don’t think it’s that outrageous of a statement.