If a person does a good job of fixing my car, but believes disease is caused by evil spirits, I may still trust his automotive expertise, but I’m not going to take his health advice.
And why would I? Why expect him to be an expert in everything just because he’s an expert in one area?
Of course, if this mechanic believes cars work because they are moved down the road by evil spirits, I’m not going to trust him to touch my car with a tool.
In the same way, no matter how smart someone may otherwise be, if they believe it’s OK (or even “necessary”) to archate, I’m not going to take their political or ethical opinions seriously. They have proved to me that they simply don’t know what they are talking about on this subject. At all. Utterly clueless.
I think the olden term for this was “he’s talking through his hat”.