Isn't the fine tuning argument ad hoc?

[Anomalocaris]

Well then why would you bother objecting to theistic arguments? The reason I'm continuing is because I think we should refine our responses to theistic arguments and our objections to their arguments, if we care about showing people why we think they're wrong and where/why their reasoning went astray.

I don't think we can prove anyone wrong as the fine-tuning is just a hypothesis. From a scientific POV, the question is, does it predict anything that can be used as evidence for its validity? So far, nothing. So it remains in the realm of all possibilities.

Actually, fine tuning is so crudely formed that it lacks any sort of foundation from which to, even in principle, produce any prediction. Yet even for absolutely the nothing it is based on and the nothing it produces it still requires a vast input of unevidenced, and open ended, extensions to known principles of how all things related to the universe works: it implies existence some higher principle at a level removed from anything shown to be required that simply permits the existence of some high level of complexity that can plan, that has intent, that has the tools to menipulate the fundmantal constants of the universe.

---

The idea behind the fine-tuning argument is very old and very primitive - "this creation has been created for us". And since such a statement wouldn't fly within the scientific methodology, the idea had to be reshaped into the hypothesis - "Different aspects of the universe have been tuned to their current values specifically to support the existence of life". Disregarding any theistic goal-shifting, we can easily consider this idea on its own merits. The line of evidence supporting this hypothesis would be:
a) Most of the universe actually being capable of supporting life.
b) Even the parts not capable of supporting life being required for the existence of parts that do.
c) Establishing that parameters outside that range are possible - though very rare and regarded as anomalies.

If this line of evidence turned out to be false, then the fine-tuning hypothesis would stand falsified.

Actually, "fine tuning" does not require the universe to be amenable to life in a lot of different places. It also does not require the parts that doesn't support life to be essential for for the parts that do.

Fine tuning says life as we know it requires such tight tolerances in the values of the fundamental constants of the universe that even just a single isolated occurrence of it in the entire universe would be astronomically improbable unless these constants were tuned to be what it is.

The bullshitness is revealed by the implicit assumption that other values of fundamental constants do not lead to other things, absolutely absent from our universe, that is just as improbable, or that the improbability that is life as we know it is in someways different from those other different improbabilities.

It is no good to throw a dart blindly and wax lyrical about how improbable it is for the dart to hit where it does, and forget a dart has to hit somewhere.