Mindreading as a fallacy

I think this is more of a cognitive bias/distortion than a fallacy. 

Mind reading is one of the reasons why communication often goes very wrong, even and sometimes especially between people who know each other. 

People think they can read other people without concretely asking them what is the matter. And a lot of research in communication has shown that people are very bad at mind reading. But most people think they can, one of the examples of this is the fundamental attribution error, other people are motivated by internal errors, but you yourself are forced by the environment and or the odds being against them.

There are two great books about this. 
- No One Understands You and What to Do About It - by Heidi Grant Halvorson Ph.D
- Mindwise Why We Misunderstand what Other Think, Believe, Feel, and Want - By Nicholas Epley

That fallacy does fit, thanks.

I will also add that this particular person's argument as to why they considered religion a mental illness: Evidence against the existence of a god is so plentiful and easily available that no reasonable person could believe that a god exists, and that a mental illness is the only explanation for a person believing something that is unreasonable.

Being charitable, you could say that certain beliefs tied to religion, like young earth creationism, are unreasonable. However, the difference I pointed out is that these beliefs are created externally and reinforced through cultural norms, whereas a person who experiences hallucinations or delusions as the result of a mental illness are generating the unreasonable beliefs within their own minds. This person didn't think this distinction mattered.

The person is claiming that believing in unreasonable things is/should be considered a "mental illness." This would lead to absurdity because virtually everyone believes in something unreasonable, and if everyone is mentally ill then the term has lost all meaning. In fact, unreason is the result of a healthy and normally functioning brain. Our brains evolved to keep us alive and help us procreate. Sometimes, these goals are antithetical to reasonable beliefs which is why we often hold unreasonable beliefs.

I would strongly agree that some instances of religious belief are actually instances of mental illness protected by the religious belief exclusion in the DSM. For instance, a sign of schizophrenia is hallucinations (e.g., two-way communicating with imaginary beings). If one were to claim they have regular two-way discussions with Jesus over tea, they might be hailed as a "miracle" whereas if they claimed to do the same with Cleopatra they would be medicated.

I conclusion, I see this person's point but it sounds to me as if they are taking an extreme position. Ironcally, being unreasonable and thus, according to their own position, having a mental illness.