Isn't the fine tuning argument ad hoc?

[Angrboda]

At this point, I'd like to throw out three things: One, fine-tuning isn't a problem that needs to be answered. It's a speculation based on a mental exercise. We don't know which, if any of the constants could have been different than they are, or how much they could vary or what the probability of different values are. All there is to fine-tuning can be summed up as 'if all of these constants could vary by a high degree in a relatively even probabablistic range with the value of none of them being determined by the value of any of the others, it would be really unlikely for any universe with specific values for its constants to exist, including ours.' Until there's evidence that the above statement is true, it isn't justifiable to actually claim that our universe is 'fine-tuned'. Positing explanations for why it could be true if it is is just thought experiments.

I think it's worth noting that the likelihood of the constants is only one half of the fine tuning argument as used by theists. The other half is an inference to design, namely, that the specifics of such tuning suggest the intervention of an intelligent, designing agent. As such, it inherits many or most of the flaws of typical intelligent design arguments designed to explain biological life. Of particular note is that, while there are measures of 'complexity' which one might borrow from communication theory and computational theory, none appear to have a ready-made fit to either design of life forms or universes; more importantly, none appear unambiguously associated with design (see critiques of Dembski's work for more on this).