I actually agree with you. It is first of all a totally legitimate question to ask, “how could X evolve”?
We are all ignorant about something, and because of that ignorance there are things that will appear implausible or even incomprehensible to us. There’s nothing wrong with asking questions about things we don’t know and don’t understand.
To someone who is not a biologist, and who has no training in evolution or molecular biology, it is perhaps completely normal to have a sort of intuitive incredulity about how evolution could even occur, or that there “just so happens to be” different genetic predispositions towards preferring or rejecting certain tastes.
But then one could of course ask out of genuine curiosity, why do biologists think something like this could evolve?
As long as we note there’s a difference between asking this question out of genuine interest and in honest ignorance of the answer, and asking it rhetorically, as if any putative answer given should be considered intrinsically implausible, if not impossible.
At best, it is certainly no defense against the original question. Granted, one asked “how could this happen” and another answered, “here’s how.” But the response is still a guess without data. Find a gene that switches the “spider organ taste preference” from one organ to another and you have a viable response to the challenge.
This is where I don’t agree, because I’d actually say that if you know enough molecular biology, for example understanding the genetics of taste receptors, and the fact that different types of tissues have different molecular components, leads to the expectation that they should have different tastes, and all animals have numerous different taste receptors that respond to different compounds.
I don’t think we actually have to bother to go and find the gene(s) responsible to have good reason to think the question doesn’t constitute the sort of challenge imagined by the creationist posing it. I think we know enough molecular biology already, to be able to say with considerable confidence, that this is the sort of thing we’d expect there to be.
Even without knowing any of that, I know from my own experience that eating different meats, including organs, that they can have wildly different tastes. Domestic pig liver is famously disliked by many people(I happen to like it though).