Can Faiths Be Incorrect?

What's Wrong is Wrong?

In a previous post, I mentioned the idea of imagining that a "religious faith" could be demonstrably incorrect. Well if faith is a belief, then I would say yes. Take for example the Flat Earth Society. Undoubtedly the people involved in the Flat Earth Society have an enormous amount of conviction that they are correct, and that the Earth is not spherical, but they are clearly and demonstrably wrong (and we shouldn't teach the controversy). 

In general few, if any, would argue that beliefs can be wrong yet here is a field where we have decided its not acceptable to say so. I don't necessarily mean whole religions being wrong, what about heretics? There are people who's faiths consist of claims that are no where to be found in, or are directly in opposition with, their holy texts and teachings. Are these people's faiths wrong? 

That Can't Be True

It would seem reasonable to say that if a faith encompasses a belief, or beliefs, which are demonstrably false, then it should follow that that faith is (at least partially) incorrect. However, religions are not sets of claims based around simple demonstrable truths and the modern edict  "all faith claims (or religions) are equal" doesn't support this basic reasoning (unless they are all assumed to be wrong). 

So which is it? Can faiths be incorrect? And what does it imply if faiths can't be incorrect? I would say they can be wrong and you would say...?