They reason within the framework of those ideas. If you accept a religious text is accurate and find an obvious contradiction then rather than rejecting the religious text you’re going to try and justify both statements as true.

So if Osiris was said to have red hair in one passage and was blond in another then they may have been referring to different people, one statement was a metaphor, he has hair of both colors at the same time, he had each at different ages, he dyes his hair at some point, etc. And of course people feel such ideas are worth fighting over.