Common logic mistake, you inverted my arrows.

I didn't say haskell is mathematical (and i do agree to your point), i said category theorists probably know haskell of all languages because of the deeper understanding/intuition they will naturally have for it. There is no denying that haskell is laid on category theory foundation and that understanding these will help you. But of course well designed things do not require you to understand their foundations to build intuition/understanding.

No, I understand what you're saying. I am saying category theorists will not have any special affinity for Haskell or vice versa. I also don't agree that Haskell is built on top of category theory. That's why I mentioned the example of idempotence.

The idea that Haskell has much to do with mathematical category theory is a meme that arises from the cargo cult of functional abstraction. It's an example of terminology overloading. There is this pattern of taking terminology from abstract algebra and category theory and using it to describe design patterns in functional programming or certain paradigms of engineering. "Monad" is one you see in Haskell which ostensibly makes it related to category theory. Another example is the idea of an "isomorphism" in web development, which doesn't mean the same thing as it does in algebra.

There's no problem with using terminology borrowed from mathematics for design patterns in engineering (and vice versa), but it should be transparent about the fact that it doesn't confer any special relation to the underlying mathematics. A category theorist and a Haskell programmer have different conceptions of what a "monad" is, and any functional design pattern modeled after an idea in category theory is going to be covered in the introduction or first chapter to a textbook. The language has more to do with lambda calculus than it does anything in actual category theory.