Realism is the default hypothesis since a CS scenario -- indeed, any scenario -- assumes realism exists, and realism does not assume that a CS exists. It is the baseline; all other hypotheses need to be supported with evidence to be considered.
Ok, working with the baseline assumption that realism exists at least somewhere, and following through Bostrom's argument, what do you disagree with?
If Bostrom's argument can't stand up to simple naysaying, then how can a reasonable person find it compelling?
You've still not outlined which part of the argument you disagree with. It's simple enough to address;
bostrom said:
This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a “posthuman” stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation.
I have no reason to accept Bostrom's argument because there is no evidence which supports it.
If one looks at the argument as one for cosmic origin (which it is within our sense of the term) then I do not see that any other alternatives are suitably endowed with evidence to be accepted.
A lack of evidence therefore would lead us to fail to accept all CO theories.
Indeed, with realism distinct from CS, and subject to different physical laws, CO
may be easily explained within the constraints of actual reality - it certainly isn't easily explained within the constraints of our universe.
With the Goldilocks enigma we are faced with the following choices;
1) our universe as it exists is an astronomical fluke
2) our universe is explained through multiverse models
3) goddidit
4) our universe is explained through CS
5) our universe can be explained without recourse for (1)-(4) but human knowledge is insufficient to do so now.
of the choices (1) and (3) are unpalatable and (5) requires in effect an appeal to human ignorance.
of the two left (2) requires the the problem is simply shifted up a level, that the complexity of the model is vastly increased and that we accept that this may be unfalsifiable.
(4) does not require greater complexity at the level of reality, provides a possibility for a simplistic CO explanation with that reality, but again requires that we accept that this may be unfalsifiable.
Given the choices (4) would appear an appealing option - regardless of counter-intuitive resistance. That's not to say one should accept it, but simply accept that it doesn't fare so badly against the alternatives.
It is unscientific and changes nothing,
How so more than alternative CO theories?