Have you coded in haskell? Really, the great-grandfather post that provoked this wasn't an attack on python, it's pointing out a difference between the type systems in ML, haskell, scala, and maybe typed racket, of the non-dependently type languages vs. all others.
I use Python + Pyramid daily; and I love it. However, I love Haskell more. Yesod/Snap/Happstack have quite a ways to go before they are on-par community and feature wise with Pyramid/Django/Rails/etc... but it's mature enough for production use.
With a little extra learning curve; it beats the pants off of Python + Pyramid + unit tests and lots of extra debugging time.
Writing unit tests is not hard. Nor is it rare or exceptional. Wrestling Haskell's type system is not necessarily easy. Overall, making programs do the right thing is a big problem in any language, including Haskell, and one hopes that any system of significant size is being tested properly whether it uses a static type system or not.
The use of a type system is not in itself an objective slam dunk for Haskell over Python or anything else.